Fidelity Leveraged Company Stock ( FLVCX) ranks as the top-performing diversified equity fund, a position it has held for the last 10 years, according to Morningstar. Its achievements are heralded in the press and investors are pouring into the fund. But if you are tempted to join the crowd, keep in mind that Fidelity Leveraged Company can be hazardous. Many shareholders have lost money in the fund.To appreciate the danger, consider an indicator that is known as investor return. This is calculated by Morningstar, and it shows how much the typical investor actually made. The investor return can be very different from the widely quoted figures for total return. If you invested in Fidelity Leveraged Stock a decade ago, your total annual return would have been 14.5%. But the typical shareholder had an investor return of only 4.0%. The reason for the gap is, most investors didn't buy and hold for the 10 years. Instead, the average dollar in the portfolio stayed invested for short periods. In 2001, the portfolio was tiny, with only $60 million in assets. Then in 2003, the fund returned an eye-popping total of 96.3%. With investors racing to buy, assets reached $7.6 billion, in 2007. Unfortunately, most investors arrived too late at the party. In 2008, the fund lost 54.5%, and assets sank to $2.8 billion as investors sold at the trough. Fidelity Leveraged Stock has such a poor investor return, partly because the fund is volatile. Holding shares of indebted companies, Fidelity sometimes soars in bull markets and then collapses in downturns. All too often, shareholders buy and sell at the wrong times. Fidelity Leveraged Stock is hardly the only top-performing fund with a poor investor return. RS Value ( RSVAX) had a total annual return of 11.0% during the past 10 years, but only delivered an investor return of 4.5%. Hotchkis and Wiley Mid-Cap Value ( HWMAX) returned 10.6% annually, and produced an investor return of 2.9%. Should you stay away from funds with poor investor returns? Not necessarily. But you should be aware of what you are buying. If you do buy a fund like Fidelity Leveraged Stock, keep your eyes open and be prepared for a rough ride. For investors who don't have strong stomachs, a better choice might be a fund like Heartland Value Plus ( HRVIX), which returned 13.8% annually during the past decade and produced an investor return of 12.0%. Because Heartland delivered a relatively steady ride, shareholders were able to hold through downturns. Another fund that outdid more than 99% of diversified funds is Delafield ( DEFIX), which had total returns of 12.5% and an investor return of 11.0%.