在歐美地區，庫藏股制度已行之多年，而台灣的庫藏股制度在2000年8月正式問世，其最主要是希望藉由其制度之施行來穩定國內股市。本研究利用2000.8.9~2004.12.31期間，上市公司利用庫藏股制度進行股票購回的事件，研究其進行購回的動機以及宣告效果的資訊內涵。實證結果如下：(1)股票購回動機方面，當公司股票被低估、公司規模較小以及過去曾經利用子公司買回母公司股票者，會傾向進行股票購回。(2)買回宣告成功向市場傳達了公司股價受低估的訊息。(3)宣告效果與股價被低估程度成顯著正相關，與宣告前五日的異常報酬及股本膨脹率成顯著負相關，且購回目的中以“為維護公司信用及股東權益所必要買回”，此購回目的的公司之宣告效果較大。

Taiwan adopted the law of treasury stock on August 2000 to stabilize the continuous slide of stock market. We study the announcements during 1999.8.9 to 2004.12.31 and try to find out not only the motives of stock repurchases but the information of the abnormal return. The result show as following: (1) The companies would intend to stock repurchase when undervaluation, the smaller firm size or the enterprise ever used the subsidiary company to repurchase the stock. (2)The stock repurchases transmit successfully the information of undervaluation to the market.(3)Abnormal return positively relates to the undervaluation, negatively relates to the abnormal return of the five days before the announcement and the inflation of the capital stock. The firm which intention of repurchase is “to conserve the credit of the firm and the rights of the shareholders” has the stronger effect of repurchasing announcement.

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