The purpose of this paper is twofold: to show how to measure profit efficiency in banking using a newly developed technique, and to use that technique to determine the effect of risk-based capital requirements on the profit performance of US banks. The measure of profit efficiency used captures deviations from profit maximization arising from technical inefficiency, caused by a lack of managerial oversight and allocative inefficiency, which is caused by managers choosing a nonoptimal mix of inputs and outputs. A leverage ratio constraint and a risk-weighted capital ratio constraint are explicitly included in the model, which allows identification of the effect on profits of those constraints. The techniques are applied to random samples of US banks for 1990, 1992, and 1994. The results indicate that allocative inefficiency is a larger source of profit loss than technical inefficiency and that the risk-based capital standards have a significant effect on bank allocative efficiency.