[UNIMED: history and characteristics of a Brazilian medical cooperative].

This article describes the organizational characteristics of the UNIMED medical cooperative in Brazil. After an overview of UNIMED's share in the current health plan market, the author analyzes its organizational structure, historical evolution, and contractual regimen with member physicians, including the formula used to calculate the payment schedule for physician services. The plan currently includes 367 local member cooperatives, operating in over 80% of Brazil's counties, with 41% of existing physicians to serve 7% of the population. The organization's history began with local cooperatives and subsequently federations, the confederation, and other companies in the group. The organizational design and dynamics favor a high degree of decentralization and autonomy, subordination of all components in the system to the physician cooperative command, and the occurrence of internal disputes and conflicts between individual interests and those of the organization.