VTSMX is Vanguard's Total Market Index fund. It's index is the Wilshire 5000. VTSMX is 70% VFINX (Vanguard's S&P500 Index fund) and 30% mid and smaller cap stocks. It is BY FAR my favorite stock mutual fund of ALL known mutual funds around.I would feel completely confortable putting ALL my stock money into VTSMX and holding it forever. In fact, it would be pretty tough to beat that simple strategy over the long run.You are lucky to have a retirement plan that offers you VTSMX. Take advangage of it!!