上市公司邊際債務策略之探討 / This thesis aims at understanding the corporate finance strategy of companies which have no or an extremely low debt to equity ratio. For this thesis, companies that have a debt-to-equity ratio less than 5% are defined as “marginal-debt” companies. We identify 167 U.S. public companies which could easily access to the financial market for debt. In order to find some explanations for the phenomenon of marginal-debt, we first examine the trade-off theory. According to the theory, it can be hypothesized that an extremely low corporate tax rate or a high marginal cost of bankruptcy could explain the minimal presence of debt for those marginal-debt companies. However, we find no evidence to accept this hypothesis. Marginal-debt companies have an average tax rate of 31.4%, compared to 29.8% for our sample of indebted companies. They also have a generally better financial health, even when deleveraging their financial ratios. Owing to that, neither bankruptcy cost explains the financial management strategy of marginal-debt. Hence, we expect this phenomenon to be purely behavioral. We therefore propose a survey questionnaire to better analyze the incentives for managers to adopt a marginal-debt strategy.. Keywords: Marginal-debt, Capital structure, Low leverage, Trade-off theory, Debt aversion