本研究旨在探討國內發行公司在IPO掛牌後1年內辦理SEO之決策因素。本研究以民國85 年至89 年間新上市（櫃）的公司為樣本進行實證，並歸納實證結果如下： 一、 國內上市（櫃）公司於IPO掛牌後首次辦理SEO之決策實證結果支持市場回饋假說，即IPO掛牌後60、120、180、240個營業日之累積超額報酬率越高（低），發行公司越（不）可能於1年內辦理SEO。惟就股價報酬波動度對之影響而言，對非電子業公司來說，IPO掛牌後60、120、180、240個營業日股價報酬波動度與發行公司辦理SEO間有顯著之負相關，但電子業公司除短天期60個營業日之波動度有顯著負相關外，較長天期之波動度則較不具解釋能力。 二、 公司規模較小、設立年限較短及負債比率較高之發行公司，較有可能在掛牌後1年內辦理SEO。另發行公司是否在IPO公開銷售時採用競價拍賣方式，及內部人持股比例等因素與發行公司是否於掛牌後1年內辦理SEO之決策間較無明顯之關係。 / The purpose of this study is to explore the factors which determine Taiwanese companies’ conducting seasoned equity offerings (SEOs) within one year after their initial public offerings (IPOs). The samples come from firms first listed on the TSEC and OTC market between 1996 with 2000. The empirical findings of this research are as follows: 1、 The factors effecting firms’ decisions on SEO support market feedback hypothesis. That is, the more abcdrmal stock returns within 60, 120, 180, and 240 transaction days after IPOs, the higher the possibility for firms to conduct a SEO. However, although the factor of stock price’s volatilities has a significantly negative relation to hi-tech firms’ SEO decisions, it has less relation to non-hi-tech firms’. 2、 Firms with smaller size, shorter age and higher debt ratio have more chance to SEO. Nevertheless, neither the factor of whether IPO in auction or not, nor the one of the insider holding ratio has a relation to companies’ SEO decisions.