If you collect your urine over 24 hours, the study staff will give you a large (3-liter) urine storage container and a small (7-ounce) plastic collection container. You will urinate into the small collection container and then pour the urine into the large urine storage container within 10 minutes after the collection. You should write down the time of the first and last collections in the large storage container and return it to the study staff at the end of the 24-hour period.