Why might it be a bad idea to invest 100% of your 401(k) into a stock index fund?
At your age, I don't think its a bad idea to invest entirely in stocks. The concern with stocks is their volatility, and at 40+ years from retirement, volatility does not concern you. Just remember that if you ever want to call upon your 401(k) for anything other than retirement, such as a down payment on a home (which is a qualified distribution that is not subject to early distribution penalties), then you should reconsider your retirement allocations. I would not invest 100% into stocks if I knew I were going to buy a house in five years and needed that money for a down payment. If your truly saving strictly for a retirement that could occur forty years in the future, first good for you, and second, put it all in an index fund. An S&P index has a ridiculously low expense ratio, and with so many years away from retirement, it gives you an immense amount of flexibility to choose what to do with those funds as your retirement date approaches closer every year. I've read a nice rule of thumb somewhere that you should consider: You should invest (100-YOURAGE)% of your money in stock The rest should be something less volatile and more liquid, so you have some money when the stock market goes down and you need some money nevertheless. So you would start with buying about 75% stock and balance your stock percentage over time by buing more secure assets to keep the stock percentage at the desired level. At some time you might need to  sell stock to rebalance and invest in more secure assets.
Conventional wisdom says (100-age) percentage of your saving should go to Equity and (age) percentage should go to debt. My advice to you is to invest (100-age) into index fund through SIP and rest in FD. You can re-balance your investment once a year. Stock picking is very risky. And so is market timing.  Of cource you can change the 100 into a other number according to your risk tolerance. A 401(k) is an investment just like any other investment. You generally get two types of return lumped into that number, but there can be more and you should read your funds prospectus carefully. If you aren't investing in direct companies, you're using mutual funds for instance, then you should read the funds prospectus to see how they handle these situations for the underlying securities they hold for you. Although I think this is the basic answer to the question as you asked. "Holding pure cash is a problem for 401K companies because they would then have follow banking rules because they would be holding your cash on their balance sheets. They don't want to be in that business. Instead, they should offer at least one option as a cash equivalent - a money market fund. This way the money is held by the fund, not by 401K administrator. Money Market funds invest in ultra-short term paper, such as overnight loans between banks and other debt instruments that mature in a matter of days. So it is all extremely liquid, as close to ""Money"" as you can get without actually being money.  It is extremely rare for a money market fund to lose value, or ""break the buck."" During the crisis of 2008, only one or two funds broke the buck, and it didn't last long. They had gotten greedy and their short term investments were a little more aggressive as they were trying to get extra returns. In short, your money is safe in a money market fund, and your 401K plan should offer one as the ""cash"" option, or at least it should offer a short-term bond fund. If you feel strongly that your money should be in actual cash, you can always stop contributing to the 401K and put the money in the bank. This is not a good idea though. Unless you're close to retirement, you'll be much better off investing in a well diversified portfolio, even through the ups and downs of the market." Ok. I'll ask - Does the job offer a 401(k)? Matching deposits? You see, the answers given depend on your risk tolerance. There are two schools of thought, one extreme will tell you not to start investing until you have the emergency fund set up, the other, start from day one. I accept there are pros and cons to either approach.  But - if you have access to a matched 401(k), even a conservative, risk-adverse approach might agree that a 100% match (on the first say 5% of your income) is preferable to saving in a low return emergency fund. If the emergency occurs, a low interest loan for the need is a cheap way out. Since the money goes in pre-tax and is matched, being able to borrow out half (IRS rules) effectively lets you borrow more than you deposited out of pocket. And the word emergency implies a low occurrence event. Deposit to the match and start the emergency fund in another account.  If no matched 401(k) at work, the other two answers are great.  Edit - To clarify, and answer a comment below - say the risk isn't just a money emergency, but job loss. $1000 deposited to the 401(k) cost $850 out of pocket, assuming 15% bracket. After the match, it's $2000. After the job loss, if this is withdrawn, if the 15% still applies (it may be 10% or even 0%) the net is $1700 less the 10% penalty, or $1500 back in your pocket.  There are those who will say they are just not comfortable running an emergency account so lean, I understand that. For the OP here, $800/mo is nearly $10,000 per year. If even half of that can be deposited pre-tax and matched, the account will grow very quickly and there would still be cash on the side. "It's a trade-off. The answer depends on your risk tolerance. Seeking higher rewards demands higher risk. If you want advice, I would recommend hiring an expert to design a plan which meets your needs. As a sample point, NOT necessarily right for anyone else...I'm considered an aggressive investor, and my own spread is still more conservative than many folks. I'm entirely in low-cost index funds, distributed as ... with the money tied up in a ""quiesced"" defined-contribution pension fund being treated as a low-yield bond. Some of these have beaten the indexes they're tracking, some haven't. My average yield since I started investing has been a bit over 10%/year (not including the company match on part of the 401k), which I consider Good Enough -- certainly good enough for something that requires near-zero attention from me. Past results are not a guarantee of future performance. This may be completely wrong for someone at a different point in their career and/or life and/or finances. I'm posting it only as an example, NOT a recommendation.  Regarding when to rebalance: Set some threshhold at which things have drifted too far from your preferred distribution (value of a fund being 5% off its target percentage in the mix is one rule I've sometimes used), and/or pick some reasonable (usually fairly low) frequency at which you'll actively rebalance (once a year, 4x/year, whenever you change your car's oil, something like that), and/or rebalance by selecting which funds you deposit additional money into whenever you're adding to the investments. Note that that last option avoids having to take capital gains, which is generally a good thing; you want as much of your profit to be long-term as possible, and to avoid triggering the ""wash sales"" rule. Generally, you do not have to rebalance very frequently unless you are doing something that I'd consider unreasonably risky, or unless you're managing such huge sums that a tiny fraction of a percent still adds up to real money." The S&P500 is an index, not an investment by itself.  The index lists a large number of stocks, and the value of the index is the price of all the stocks added together. If you want to make an investment that tracks the S&P500, you could buy some shares of each stock in the index, in the same proportions as the index.  This, however, is impractical for just about everyone. Index mutual funds provide an easy way to make this investment.  SPY is an ETF (exchange-traded mutual fund) that does the same thing. An index CFD (contract for difference) is not the same as an index mutual fund.  There are a number of differences between investing in a security fund and investing in a CFD, and CFDs are not available everywhere. Some index funds offer lower expense ratios to those who invest large amounts of money. For example, Vanguard offers Admiral Shares of many of its mutual funds (including several index funds) to individuals who invest more than $50K or $100K, and these Shares have lower expense ratios than the Investor shares in the fund. There are Institutional Shares designed for investments by pension plans, 401k plans of large companies etc which have even lower expenses than Admiral Shares. Individuals working for large companies sometimes get access to Institutional Shares through their 401k plans.  Thus, there is something to gained by investing in just one index fund (for a particular index) that offers lower expense ratios for large investments instead of diversifying into several index funds all tracking the same index. Of course, this advantage might be offset by failure to track the index closely, but this tracking should be monitored not on a daily basis but over much longer periods of time to test whether your favorite fund is perennially trailing the index by far more than its competitors with larger expense ratios. Remember that the Net Asset Value (NAV) published by each mutual fund after the markets close already take into account the expense ratio. "As Dheer pointed out, the top ten mega-cap corporations account for a huge part (20%) of your ""S&P 500"" portfolio when weighted proportionally. This is one of the reasons why I have personally avoided the index-fund/etf craze -- I don't really need another mechanism to buy ExxonMobil, IBM and Wal-Mart on my behalf. I like the equal-weight concept -- if I'm investing in a broad sector (Large Cap companies), I want diversification across the entire sector and avoid concentration. The downside to this approach is that there will be more portfolio turnover (and expense), since you're holding more shares of the lower tranches of the index where companies are more apt to churn. (ie. #500 on the index gets replaced by an up and comer). So you're likely to have a higher expense ratio, which matters to many folks." The alternative isn't too bad. Invest in a regular account. The dividends and cap gains will see favorable tax treatment. In my opinion, much of the magic of the retirement account is with 401(k) matched deposits.  The benefit you'll miss is the long term opportunity to skim income off the top, at say, 25%, have it grow, and then withdraw it at a much lower average tax rate. If that benefit doesn't outweigh the fear of the 10%, stick with my first thought above. Why is that? With all the successful investors (including myself on a not-infrequent basis) going for individual companies directly, wouldn't it make more sense to suggest that new investors learn how to analyse companies and then make their best guess after taking into account those factors? I have a different perspective here than the other answers.  I recently started investing in a Roth IRA for retirement. I do not have interest in micromanaging individual company research (I don't find this enjoyable at all) but I know I want to save for retirement. Could I learn all the details? Probably, as an engineer/software person I suspect I could. But I really don't want to. But here's the thing: For anyone else in a similar situation to me, the net return on investing into a mutual fund type arrangement (even if it returns only 4%) is still likely considerably higher than the return on trying to invest in stocks (which likely results in $0 invested, and a return of 0%). I suspect the overwhelming majority of people in the world are more similar to me than you - in that they have minimal interest in spending hours managing their money. For us, mutual funds or ETFs are perfect for this. The problem is that short-term trends are really unpredictable.  There is nobody who can accurately predict where a fund (or even moreso, a single stock or bond) is going to move in a few hours, or days or even months. The long-term trends of the entire market, however, are (more or less) predictable.  There is a definite upward bias when you look at time-scales of 5, 10, 20 years and more.  Individual stocks and bonds may crash, and different sectors perform differently from year to year, but the market as a whole has historically always risen over long time scales. Of course, past performance never guarantees future performance.  It is possible that everything could crash and never come back, but history shows that this would be incredibly unlikely.  Which is the entire basis for strategies based on buying and holding (and periodically rebalancing) a portfolio containing funds that cover all market sectors. Now, regarding your 401(k), you know your time horizon.  The laws won't let you withdraw money without penalty until you reach retirement age - this might be 40 years, depending on your current age.  So we're definitely talking long term.  You shouldn't care about where the market goes over a few months if you won't be using the money until 20 years from now. The most important thing for a 401(k) is to choose funds from those available to you that will be as diverse as possible.  The actual allocation strategy is something you will need to work out with a financial advisor, since it will be different for every person.  Once you come up with an appropriate allocation strategy, you will want to buy according to those ratios with every paycheck and rebalance your funds to those ratios whenever they start to drift away.  And review the ratios with your advisor every few years, to keep them aligned with large-scale trends and changes in your life. Unless that 401K has very low expense ratios on its funds, you should roll it into an IRA and choose funds with low expense ratios. After rolling it over you should not take the 10% penalty and use it to purchase a home.  Unless you use that home as an income property, it is unlikely to provide you more than a 1% inflation-adjusted rate of return given historical data.  The S&P 500 is about 4% adjusted for inflation.  And that money currently in your 401(k) is for your retirement - your future.  Don't borrow against your future.  Let compound interest do its work on that money. The value of a house is in the rent you aren't paying to live somewhere and there are a lot of costs to consider.  That doesn't mean don't buy.  It just means buy wisely. If you are currently maxing out your 401(k), you may consider cutting back to save for your down payment.  Other than that I wouldn't touch retirement money unless it was a dire financial emergency. "The question you should be asking yourself is this: ""Why am I putting money into a 401(k)?"" For many people, the answer is to grow a (large) nest egg and save for future retirement expenses. Investors are balancing risk and potential reward, so the asset categories you're putting your 401(k) contribution towards will be a reflection on how much risk you're willing to take. Per a US News & World Report article: Ultimately, investors would do well to remember one of the key tenants   of investing: diversify. The narrower you are with your investments,   the greater your risk, says Vanguard's Bruno: ""[Diversification]   doesn't ensure against a loss, but it does help lessen a significant   loss."" Generally, investing in your employer's stock in your 401(k) is considered very risk. In fact, one Forbes columnist recommends not putting any money into company stock. FINRA notes: Simply stated, if you put too many eggs in one basket, you can expose yourself to significant risk. In financial terms, you are under-diversified: you have too much of   your holdings tied to a single investment—your company's stock.   Investing heavily in company stock may seem like a good thing when   your company and its stock are doing well. But many companies   experience fluctuations in both operational performance and stock   price. Not only do you expose yourself to the risk that the stock   market as a whole could flounder, but you take on a lot of company   risk, the risk that an individual firm—your company—will falter or   fail. In simpler terms, if you invest a large portion of your 401(k) funds into company stock, if your company runs into trouble, you could lose both your job AND your retirement investments. For the other investment assets/vehicles, you should review a few things: Personally, I prefer to keep my portfolio simple and just pick just a few options based on my own risk tolerance. From your fund examples, without knowing specifics about your financial situation and risk tolerance, I would have created a portfolio that looks like this when I was in my 20's: I avoided the bond and income/money market funds because the growth potential is too low for my investing horizon. Like some of the other answers have noted, the Target Date funds invest in other funds and add some additional fee overhead, which I'm trying to avoid by investing primarily in index funds. Again, your risk tolerance and personal preference might result in a completely different portfolio mix." The expense fees are high, and unfortunate. I would stop short of calling it criminal, however.  What you are paying for with your expenses is the management of the holdings in the fund. The managers of the fund are actively, continuously watching the performance of the holdings, buying and selling inside the fund in an attempt to beat the stock market indexes. Whether or not this is worth the expenses is debatable, but it is indeed possible for a managed fund to beat an index.  Despite the relatively high expenses of these funds, the 401K is still likely your best investment vehicle for retirement. The money you put in is tax deductible immediately, your account grows tax deferred, and anything that your employer kicks in is free money.  Since, in the short term, you have little choice, don't lose a lot of sleep over it.  Just pick the best option you have, and occasionally suggest to your employer that you would appreciate different options in the future. If things don't change, and you have the option in the future to rollover into a cheaper IRA, feel free to take it. "Can you easily stomach the risk of higher volatility that could come with smaller stocks? How certain are you that the funds wouldn't have any asset bloat that could cause them to become large-cap funds for holding to their winners? If having your 401(k) balance get chopped in half over a year doesn't give you any pause or hesitation, then you have greater risk tolerance than a lot of people but this is one of those things where living through it could be interesting. While I wouldn't be against the advice, I would consider caution on whether or not the next 40 years will be exactly like the averages of the past or not. In response to the comments: You didn't state the funds so I how I do know you meant index funds specifically? Look at ""Fidelity Low-Priced Stock"" for a fund that has bloated up in a sense. Could this happen with small-cap funds? Possibly but this is something to note. If you are just starting to invest now, it is easy to say, ""I'll stay the course,"" and then when things get choppy you may not be as strong as you thought. This is just a warning as I'm not sure you get my meaning here. Imagine that some women may think when having a child, ""I don't need any drugs,"" and then the pain comes and an epidural is demanded because of the different between the hypothetical and the real version. While you may think, ""I'll just turn the cheek if you punch me,"" if I actually just did it out of the blue, how sure are you of not swearing at me for doing it? Really stop and think about this for a moment rather than give an answer that may or may not what you'd really do when the fecal matter hits the oscillator. Couldn't you just look at what stocks did the best in the last 10 years and just buy those companies? Think carefully about what strategy are you using and why or else you could get tossed around as more than a few things were supposed to be the ""sure thing"" that turned out to be incorrect like the Dream Team of Long-term Capital Management, the banks that were too big to fail, the Japanese taking over in the late 1980s, etc. There are more than a few times where things started looking one way and ended up quite differently though I wonder if you are aware of this performance chasing that some will do."