Management forecasts are an important source of information for the Japanese stock market. In this paper, we use management forecast error as a proxy for disclosure quality to investigate the relationship between disclosure quality and idiosyncratic risk. We find that management forecast error is positively related to idiosyncratic risk, suggesting that high-quality public information reduces idiosyncratic risk. Furthermore, we present evidence that management forecast error is less positively related to idiosyncratic risk in relatively good information environments.