Mutual funds are typically grouped by their investment objectives or the style of their managers. We propose a new empirical to the determination of manager style . This approach is simple to apply, yet it captures nonlinear patterns of returns that result from virtually all active portfolio management styles. Our classifications are superior to common industry classifications in predicting cross-sectional future performance, as well as past performance, and they also outperform classifications based on risk measures and analogue portfolios. Interestingly, growth funds typically break down into several categories that differ in composition and strategy.