Vesting is how much of the money the company put in you own. It usually goes up by 20% per year so after 1 year you keep 20% and they take back 80%, after 2 years you keep 40%, up to 5 years where you now get to keep it all. This is only for money they put in, you always keep 100% of the money you put in. First, do you have the option of leaving it where it is? Some companies say yes, some say no. If you can, and you are happy with the investment choices they offer and the fees they charge, leave it there at least for now. If you get another job with a 401k plan you can roll it over to that plan. You can also roll it over to an IRA at basically any financial institution you choose, now if you have to move it immediately or any time later you decide to. As others said, look at the investment choices and the fees. If you roll it over, always have the 401k plan send it directly to the new place, DO NOT have them send you a check. If they do, you have a limited time to get it to an IRA or the IRS comes after you for taxes and penalty.