ABSTRACT: We develop a model to show that transparent accounting can worsen the asset substitution effect of debt. This negative effect can outweigh the usual positive effect of transparency. We demonstrate this point by comparing pure historical cost accounting to the conservatively skewed accounting regime of lower-of-cost-or-market (LCM). In a market with asymmetric information, the two regimes lead to different degrees of transparency. The more transparent LCM regime produces more efficient results for firms with lower debt levels, while the opaque rule of pure historical cost accounting is preferable for higher debt levels. We explore the implications of this result for the firm's optimal capital structure.