公司的成長，需要靠有利的投資；而有利投資之進行，則有賴公司內外部融資之支持。在完美的資本市場裏，公司可以不擔心融資問題，只要有獲利機會，皆可進行投資；但在不完美資本市場裏，不見得所有公司都有充分資金支持投資的進行，因此，投資與內外部融資決策可能相互影響。 國外文獻對於投資、股利與外部融資三大決策間之交互影響有不少實證研究，主要是探討資本市場不完美程度是否足以使上列三決策必需同時決定，所採用之計。量方法包括0LS、2SLS、3SLS及SUR等，YANG( 1989 )首次採用二階移轉聯立方程式( Two-Stage Switching Simultaneous Equation)檢定美國上市公司公司現金增資決策下上列三決策之交互影響。 本文亦採用YANG使用之方法，探討台灣上市公司現金增資決策下，三大決策交互影響，以決定台灣資本市場不完美程度。本文發現，台灣上市公司是否現金增資，除了股利與舉債融資決策對投資決策之影響會有所不同外，其他交互影響大致上無顯著差異。台灣上市公司股利政策大致上不影響投資決策，但公司舉債則正面影響到公司之投資決策，因此，MM( l958 )的公司價值不受融資決策之說不受到支持；而Dhrymes及Kurz1967)的股利與投資決策相互爭取公司有限資金之理論亦無強烈證據支持。此外，本文亦發現公司採取溫和調整的股利政策。

This paper uses financial data of public firms in the Taiwan stock market to study the interaction among the investment, dividend and financing decisions of firms. The methodology used by Yang (1989) is used in this paper, that is the two-stage switching simultaneous equation system pro-posed by Lee, Maddala and Trost ( 1979 ). Given that a firm issue new shares or not, the interaction among the three decisions are examined. The results do not provide consistent evidence that the dividend policy of a firm has impacts on its investment policy, whether a firm issues new shares or not. The proposition by Dhrymes and Kurz ( 1967 ) that a firm's investment decision competes with its dividend decision for limited source of funds does not gain support either. The increase in long term debt does facilitate the investments. MM's ( 1958 ) proposition that a firm's value should be independent of its financing dicisions is rejected here. Firms are found to adopt dividend smoothing policy.