本文旨在探討新上市股票開放信用交易對股價報酬波動與成交量的影響，分別就個股及整體新上市股兩方面來探討。波動指標採用ABDL (2001)提出的日內股價報酬累積波動度。本文也探討開放信用交易前後之股價波動、成交量與產業別、公司規模大小是否有關聯性。實證結論顯示：
一、在股價報酬波動方面，就個別新上市股票而言，隨著信用交易開放後的時間增長，開放信用交易前後之波動有顯著差異的個數佔多數。但就整體新上市股票而言，開放信用交易前後之股價波動性並無顯著差異。
二、在成交量方面，就個別新上市股票而言，開放信用交易前後成交量有顯著差異個數居多，其中大部分股票的成交量變大；就整體新上市股票而言，開放信用交易前後初期之成交量並無顯著差異，但隨著信用交易開放後時間的增長成交量有顯著增大。
三、不同公司規模之開放信用交易前後波動度差異與否無顯著不一致，但不同產業別之波動度差異與否則有顯著不一致，即非電子類股的波動度在開放信用交易前後初期無顯著差異比例相對較高；開放信用交易前後之成交量差異與否則和產業別、公司規模無顯著不一致。
　　總之，新上市股票開放信用交易並不會改變股價的變異程度。但隨著開放時間的增長，成交量卻顯著增大，意味著有愈多的投資者參與股票市場，足見開放信用交易確有活絡交易，滿足投資人擴大信用之功能。

　　The purpose of this study is to investigate the effects of the opening of margin trading for IPO stocks on the stock price volatility and trading volume, both individually and totally.The index of the volatility applied in the study is intraday cumulative return volatility of ABDL (2001). The relationship between the differences of the price volatility or trading volume for diverse industries or corporation sizes is also discussed. The empirical results in the study are as follows:
1. With respect to the price volatility, there exists a significant difference between pre- and post-margin trading for most individual stocks. However, no such relationship exists for the whole stocks.
2. With respect to the trading volume, there exists a significant difference between pre- and post-margin trading for most individual stocks and most of their trading volume becomes larger. The relationship also exists for the whole stocks.
3. There exists no significant relationship between the differences of the price volatility of stocks for diverse corporation sizes, but not for diverse industries. The volatility differences of most non-quasi-electrical stocks aren’t significant in the initial stage of pre- and post-margin trading. No relationship exists between the differences of the trading volume of stocks for diverse industries or corporation sizes.
　　In sum, the price variations of stocks can’t be changed after the opening of margin trading for IPO stocks. But as the research period become longer, the trading volume is significantly larger. It means that more investors participate in the market. The opening of margin trading for IPO stocks is benefit for increasing the frequency of trading and expanding investors’credit.

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