本研究主要係探討我國上市公司現金增資除權制度之變革，對於股票市場股價行為的影響。 本研究之研究重點在於新、舊除權制度之下，上市公司現金增資時，是否皆存在異常報酬的情形？二種制度之下，股價行為是否有明顯的不同？還是股價行為不因新、舊除權制度之不同而有所不同？此外，以往所做之研究僅包括新、舊制度之下除權日前後數日之股價表現，本研究欲探討除了除權日之外，其他日期或分類因素對於股價表現是否會有影響，藉以探討制度之改變其影響的層面及時點，這些欲探討之因素有：產業別因素、增資額度因素、宣告日，以及證期會核准日等。 / Abstract This study attempts to examine Taiwan's market reactions of seasoned new issues under the different ex-right processes. In Taiwan , it takes about two or three months to issue new stocks and it's not convenient for both issuers or investers . Before the change of the ex-right process, while public companies issue new stocks , the ways to determine the issue price are different between Taiwan and the United States or Japan. SEC has changed the ex-right process since Oct 17,1994. The study selects samples from the period between 1991 to 1998, total 419 samples , the empirical findings of this study can be summarized as follows: n Significant difference of market reactions can be found on the ex-right date and announced day, under both the new and old ex-right process. n No significant difference of market reactions can be found on the approved day. n Significant difference of market reactions can be found if grouped by industry.