We use a time-series GARCH approach to investigate the January effect in the Japanese stock market. We find that the January effect is more pronounced before the anomaly is released to the public. We provide some evidence that the decline in the degree of January effect can be partially attributed to the long-term Japanese economic recession during the entire 1990s. We find that volatility risk is higher in January. But the higher volatility risk is not the primary cause for January effect. We find some evidence that risk compensation can explain the average market returns in January.