本研究以台灣上市公司為樣本資料，在考慮總體經濟、產業因素、信用風險、及公司規模的差異後，探討公司之資本結構(capital structure)和公司價值、經營績效、獲利能力及股價報酬之關聯性。本研究以負債權益比(debt-to-equity ratio)為代理變數，實證結果發現，資本結構對公司績效變數皆呈現非線性的「微笑曲線」(smile curve)，亦即企業在資本結構的採用上有低度及高度財務槓桿的兩極化傾向，長期負債佔總資本的轉折點約在0.4至0.6之間。對不被金融機構容許過高負債的多數企業而言，使用高度的財務槓桿可能對公司績效產生負向的影響，推論對這些企業而言，採用低度財務槓桿的穩健經營策略，不僅可避免舉債偏高所產生財務危機相關成本，並可保護未來的利潤，此項結果與支持低度財務槓桿的「特權價值假說」(franchise-value hypothesis)相符。另一方面，實證結果亦顯示，對某些公司而言，高度財務槓桿對公司績效可能產生正向的影響，推論因其高風險的經營屬性，高度財務槓桿的使用可產生高報酬，是故在高度舉債經營下可以增加公司價值，此項論點與支持高度財務槓桿的「效率風險假說」(efficiency-risk hypothesis)相符。

This study investigates the relationship between capital structure and corporate performance. Specifically, we explore how capital structure influences firm value, operating performance, corporate profitability, and stock return. The empirical investigation is conducted with the use of ordinary least square (OLS) method on the sample of Taiwan publicly listed companies for a time period of 2003-2007. The regression results suggest that the graphical relationships between capital structure and corporate performance variables appear to be a smile curve, providing strong empirical evidence for two controversial hypotheses, the franchise-value hypothesis and the efficiency-risk hypothesis, suggested by Berger and Patti (2006). The franchise-value hypothesis states that more efficient firms tend to choose relatively high equity ratios to protect the future income derived from high profit efficiency, while the efficiency-risk hypothesis implies that more efficient firms tend to choose relatively low equity ratios in order to protect the firm against financial distress. The turning point of the smile curve is found to be situated at 0.4-0.6 as a ratio of long-term debt to total capital. In addition, the study finds no evidence that capital structure would have an impact on stock return.