In the implementation/consolidation process of the Brazilian Single Health System (SUS), hospitalization deserves special attention from the local management. This descriptive study identifies, through qualitative data, factors that explain variations in the number of hospitalizations processed and paid by the Municipal Health Department of Ribeirão Preto, Brazil. Data were collected through interviews with people who produce/use information regarding hospitalizations and then analyzed according to Bardin's (1979) thematic content analysis. As the major explanatory factors for the variation in hospitalizations, interviewees indicated changes in the demographic structure, low problem solving ability in basic care services, introduction of hospitals in the health system, technological incorporation, and the administrator's role in the local health system. It is the responsibility of the administrator, by using scientific instruments associated to human interaction, to regulate, control, and evaluate hospitalizations, planning health care according to the users' needs and organizing the system so as to reach satisfactory results.
health manager; hospitalization; single health system; hospital information systems