Three problems have restricted the use by sociologists of social exchange theory. The first is the risk of utilitarianism, present in the perspective followed by Homans. The second problem is the inability of social exchange theory fully to achieve its goals: in particular, its failure to resolve the issue of money in social exchange. The third problem is social exchange theory's inability to pass from explanation of elementary behavior to that of social structures and institutions. This essay shows how these difficulties can be overcome by incorporating social exchange theory into a Parsonian framework. Development is given to Parsons's notion of influence as a generalized medium of exchange which circulates in the social system and which, for sociology, performs the same functions as money in economics. The analogies between the conceptual systems of economics and sociology go beyond the simple notion of exchange, which, in fact, constitutes a key concept with which to study the workings of the social system.