This paper examines whether predictable seasonal patterns in firm fundamentals generate time variation in stock returns. Our findings indicate that stock returns are counterseasonal. Specifically, a long-short strategy of buying low-sales season stocks and shorting high-sales season stocks produces an annual alpha of 8.4% (14.5% over the last decade). This seasonal effect has a relatively high Sharpe ratio and occurs independently of previously documented seasonal anomalies. We analyze several possible hypotheses for this phenomenon.