本研究以管理當局前期預測有用性作為衡量財務預測可靠程度的代理變數，將本期原編財務預測區分為較有用與較不具參考價值的財務預測，採用Mishkin (1983)理性預期檢定架構，測試股價對原編強制性財務預測反應之效率性。實證結果顯示，較不具參考價值的財務預測（前期預測有用性低）與未來盈餘間關聯，與股價中所反應之未來盈餘一致，但股票市場低估較有用的原編強制性財務預測所含未來盈餘的預期，顯示市場對依誠信原則編製之有用的強制性財務預測信心不足，未完全據以制定投資決策。進一步按原編強制性財務預測高低形成五個投資組合，觀察最高組與最低組的投資組合能否賺取異常報酬，作為前述市場對強制性財務預測反應效率性實證結果的佐證。實證結果與Mishkin檢定結果相符：根據較有用財務預測預測值高低形成之最高組與最低組的投資組合則分別產生顯著正與負的異常報酬。較不具參考價值財務預測最高（低）組形成的投資組合未能賺得顯著正（負）的異常報酬，也未產生顯著負（正）的異常報酬，市場並未受這些財務預測誤導。 This study examines the efficiency of stock price responses to the initial mandatory financial forecasts issued by listed companies. The market responses to initial management forecasts are examined under Mishkin (1983) framework. The rationality of the stock price responses suggests the future earnings implications of management forecasts are embedded in prices. Mishkin test results indicate the existence of excess returns from a trading rule based on these management forecasts. The samples are grouped into two subsamples based on a measure of management forecast quality. The Mishkin test results show that, for low quality subsample, future earnings implication embedded in prices are indifferent to the future earnings implication in the initial mandatory financial forecasts. However, for high quality subsample, the Mishkin test results show that future earnings implication embedded in prices are smaller than the future earnings implication in the initial mandatory financial forecasts, suggesting that the market is conservative to the future earnings implications of high quality mandatory financial forecasts. Portfolio tests show that under-reactions to high quality management forecasts can be exploited via forming a hedged portfolio. Low quality forecasts generate neither excess returns nor excess losses. The latter corroborating evidence suggests that the market is not fooled by low quality forecasts.