This paper presents a model and some highly tentative empirical estimates of the social costs of monopoly and monopoly-inducing regulation in the United States. Unlike the previous studies, it assumes that competition to obtain a monopoly results in the transformation of expected monopoly profits into social costs. A major conclusion is that public regulation is probably a larger source of social costs than private monopoly. The implications of the analysis for several public policy issues, such as appropriate policy toward mergers and price discrimination, are also discussed.