In the theory of the firm it is conventional to regard firms as (total
) profit-maximizing institutions. In this paper it is shown that the i
nterdependence among firms that is characteristic of monopolistic comp
etition makes it plausible for them also to choose to maximize the rat
e of profit on capital advanced. For a homogeneous product with inelas
tic total demand, such as gasoline retailing, firms acting as rational
agents, facing fixed costs in a homogeneous spatial market, and choos
ing to set prices under rate of profit-maximization can achieve higher
total profits than firms operating under total profit-maximizing obje
ctives.