In resource-poor countries, district health managers (DHM) have gained importance as health systems have become decentralized. Although the roles and key functions of DHM have been described in the literature, there appears to have been no analysis of what they are really doing. In this context, the knowledge and job performance of 218 DHM from nine Latin American countries were investigated. The study was based on 12 performance indicators, two self-administered questionnaires (which included internal consistency tests), formal and informal, check interviews in the work place, and direct observations of the DHM. The DHM investigated were found to be particularly weak in systems management (community involvement and intersectoral co-operation), monitoring activities and the systematic organization of meetings. They were rarely involved in the identification of priority health problems or of high-risk groups, and failed to use health-service indicators sufficiently for the analysis of the district health system. The managers were stronger in relation to the organization of technical meetings and the development and implementation of local health plans. Factors associated with good management performance were a favourable organizational structure (including written job descriptions and support from the authorities), 'decision power' (i.e. the ability to select and appoint new staff ) and a good knowledge of the local situation. In Latin America, at least, DHM need to be better prepared, supervised and supported.