本研究探討雷曼兄弟倒閉事件對美國金融機構股價報酬率所帶來的傳染效果。我們的研究結果顯示，持有雷曼兄弟股份的金融機構受到較顯著的影響，而且在股東當中以商業銀行及投資銀行所受到之衝擊最為顯著，而投資銀行受影響之程度又高於商業銀行。我們也發現，金融機構對雷曼兄弟的持股比例愈高，其股價受到雷曼倒閉危機影響之程度亦愈高。此外，一些規模較小的金融機構在一些事件中亦呈現了顯著的反應，顯示在某種程度上，雷曼兄弟危機事件在金融產業當中引發了傳染效果（Contagion effect）。我們的實證結果也顯示，美國政府此次未介入救援雷曼兄弟的做法，被市場解讀為金融機構不再是「太大而不能倒（too-big-to-fail）」。 / We examine the contagion effect of Lehman Brother’s bankruptcy on US financial institutions’ stock returns. Our results show that financial institutions which held Lehman’s shares were affected more significantly. Furthermore, within Lehman’s shareholders, commercial banks and investment banks were affected most significantly, and impacts on investment banks were more significantly than commercial banks. We also find that the higher financial institution’s ownership percentage of Lehman was, the more its stock price was affected. Besides, some smaller financial institutions were also influenced significantly in some events, to some extent, implying a contagion effect in the financial sector. Our empirical results also indicate that the way that US government not to rescue Lehman Brother was perceived by the market that no financial institutions are too-big-to-fail.