Should I list all my research on a CV? Or should I only put the most significant medical research trials? I am updating my CV and applying to jobs in medical research. I am wondering if I should put all the trials that I have worked on with various other doctors or just the most significant ones?  I have like 40 research trials I have worked on and it seems immodest and overdone.
Ah, this is a good question!

Unlike a resumé, in which one includes only the experiences/skills that are relevant to the position being applied for, a CV is meant to document all  reasonable academic endeavors and accomplishments. In some cases, lines on your CV will be only loosely related to your main research interest; my CV for instance includes several co-authored papers I am not particularly keen on.

I don't know that there is any hard-and-fast 'rule' stating your CV must be complete, good and bad, but it has been my impression over the years that one includes pretty much everything.  If you've ever wondered why your department chair's CV is 35 pages long, now you know why.