The paper is based on a study of institutions dealing with the Parisian economy in the nineteenth century (Chamber of Commerce, Tribunal de commerce, Municipal Council, and councils of the Banque de France). Most of their members were at the same time businessmen. Having studied their personal careers and ties and their influence on the economic policy, I will define different forms of networks and look for evidence of their effects. The main aims of the paper are to assess the changing weight of private ties on individual careers, and to elaborate on the notion of institutional networks: what may shared membership allow? what do institutions exchange? The emphasis will be put on information exchanges. By questioning the clichés of business controlling politics, family controlling business etc., this paper aims at building bridges between business history, social history, and institutional history.