本研究之目的在探討風險轉移之代理成本與內部最適資本結構的關係。 如果代理 成本函數嚴格遞增，可與負債之有利處抵消，最適資本結構中便包含負債與業主權益。使用 圖形法分析負債額與其遞際代理成本之關係，發現此函數並非嚴格遞增。在某些特定條件下 ，此函數也許嚴格遞增，但仍未必能造成內部最適資本結構，所以，針對此部份之代理成本 而言，並無法解釋內部最適資本結構的現象。

　　　　　The purpose of this paper is to investigate the relationship between the interior capital structure and the agency costs of debt from risk shifting. If the agency cost function is strictly increasing in the debt amount, it can be traded off at the margin against the benefits of debt. Then an interior capital structure is optimal. Using a graphical approach, we analyze the relationship between the marginal agency costs of debt and the leverage ratio. We find that this relationship may not be strictly increasing with the face value of debt. Under some special cases regarding to the production possibility set and the distribution of the return, the agency cost function may be strictly increasing. But still the existence of the interior optimal capital structure remains ambiguous. In general, therefore, this part of the agency cost argument alone does not lead to an interior solution in capital structure. Various arguments based upon the agency costs of risk shifting problem need to be re-examined more carefully.