The central question this article addresses is: What are the functions of street vendor organizations? The study of street vending in Mexico City shows that vendor organizations perform mainly two central functions. (1) Organizations as negotiators or deal-makers; street vendors choose to become members of these organizations as a means to overcome red tape or complex bureaucracies. (2) Organizations as managers of social assets; organizations limit membership and access to informal markets and manage conflicts among vendors. The article shows that social capital, family, friends, etc., play an important role among street vendors whenever access to stalls in the informal market is at stake. The article raises questions regarding the way policies to formalize street vending are being implemented. Governments are attempting to control and regulate street vendors without taking into account their organizations. The article points out that future policies need to be designed in such a way that government and social institutions, like street vendor organizations, share responsibilities for the smooth functioning of informal markets. Finally, the article concludes that social institutions could represent an efficient solution to problems such as service delivery and others that people in developing countries face. (C) 1999 Elsevier Science Ltd. All rights reserved.