Vanguard Total Stock Market Index Fund Investor Shares (VTSMX) is the whole thing - large, mid and small - so you'd not need to have the other two as they'd be redundant to what is already in VTSMX. Not sure why you'd choose to hold three different funds when one would do the same thing much more elegantly. And cheaper expense ratio - the two you listed have 0.24% expense ratios, while VTSMX is 0.17%...