Path analysis method is in use in this study to examine the relationships among the mutual fund performance, the fund size, fund family size, expense ratio, turnover rate, volatility, ranking and Jensen index. The research sampled 8,953 US equity and bond funds from 2001 to 2004. Our empirical results confirm that mutual fund ranking, Jensen index and volatility are key factors to affect equity and bond funds' performance and thus they could be useful indicators of funds selection. There is no significant relationship between turnover rate and the performance of equity funds or bond funds. Nevertheless, other factors show different impacts on various types of mutual funds.