Multiple activities may be separated financially, allowing each to optimize its financial structure, or combined in a firm with a single optimal financial structure. We consider activities with nonsynergistic operational cash flows, and examine the purely financial benefits of separation versus merger. The magnitude of financial synergies depends upon tax rates, default costs, relative size, and the riskiness and correlation of cash flows. Contrary to accepted wisdom, financial synergies from mergers can be negative if firms have quite different risks or default costs. The results provide a rationale for structured finance techniques such as asset securitization and project finance.

The joint determination of capital structure and investment risk is examined. Optimal capital structure reflects both the tax advantages of debt less default costs ( Modigliani and Miller (1958, 1963) ), and the agency costs resulting from asset substitution ( Jensen and Meckling (1976) ). Agency costs restrict leverage and debt maturity and increase yield spreads, but their importance is small for the range of environments considered. Risk management is also examined. Hedging permits greater leverage. Even when a firm cannot precommit to hedging, it will still do so. Surprisingly, hedging benefits often are greater when agency costs are low.

This article examines corporate debt values and capital structure in a unified analytical framework. It derives closed-form results for the value of long-term risky debt and yield spreads, and for optimal capital structure, when firm asset value follows a diffusion process with constant volatility. Debt values and optimal leverage are explicitly linked to firm risk, taxes, bankruptcy costs, risk-free interest rates, payout rates, and bond covenants. The results elucidate the different behavior of junk bonds versus investment-grade bonds, and aspects of asset substitution, debt repurchase, and debt renegotiation.

This article examines corporate debt values and capital structure in a unified analytical framework. It derives closed‐form results for the value of long‐term risky debt and yield spreads, and for optimal capital structure, when firm asset value follows a diffusion process with constant volatility. Debt values and optimal leverage are explicitly linked to firm risk, taxes, bankruptcy costs, risk‐free interest rates, payout rates, and bond covenants. The results elucidate the different behavior of junk bonds versus investment‐grade bonds, and aspects of asset substitution, debt repurchase, and debt renegotiation.

Transactions costs invalidate the Black‐Scholes arbitrage argument for option pricing, since continuous revision implies infinite trading. Discrete revision using Black‐Scholes deltas generates errors which are correlated with the market, and do not approach zero with more frequent revision when transactions costs are included. This paper develops a modified option replicating strategy which depends on the size of transactions costs and the frequency of revision. Hedging errors are uncorrelated with the market and approach zero with more frequent revision. The technique permits calculation of the transactions costs of option replication and provides bounds on option prices.

Transactions costs invalidate the Black-Scholes arbitrage argument for option pricing, since continuous revision implies infinite trading. Discrete revision using Black-Scholes deltas generates errors which are correlated with the market, and do not approach zero with more frequent revision when transactions costs are included. This paper develops a modified option replicating strategy which depends on the size of transactions costs and the frequency of revision. Hedging errors are uncorrelated with the market and approach zero with more frequent revision. The technique permits calculation of the transactions costs of option replication and provides bounds on option prices.