Analysis of broad samples of value-weighted and equal-weighted returns of U.S. equities documents that abnormally high rates of return on small-capitalization stocks continue to be observed during the month of January. This January effect in small-cap stock returns is remarkably consistent over time and does not appear to have been affected by passage of the Tax Reform Act of 1986. This finding brings new perspective to the tax-loss selling hypothesis and suggests that behavioral explanations are relevant to the January effect. After a generation of intensive study, the January effect continues to present a serious challenge to the efficient market hypothesis.