INTRODUCTION: Studies about the impact of hospitalizations for diabetes in the Private Health System are unknown in Brazil. OBJECTIVES: To estimate the dimension of hospitalization for diabetes mellitus (DM) and its complication in the private health care system in Ribeirão Preto (RP) region, São Paulo. METHODS: Hospitalization data from 26 private hospitals of RP region (26 cities) were collected from a database of Social Medicine Department from São Paulo University (CPDH-Centro de Processamento de Dados). These data comprised an average of 35,964 admissions per year (2006-2007) of patients from 30 to 74 years old. Combinations of DM prevalence and hospitalization relative risk for chronic complications and general medical conditions (GMC) were added to DM first-listed hospitalizations (attributable risk methodology). The chronic complications diagnoses were divided into five groups: neurological disease, peripheral vascular disease (PVD), cardiovascular disease (CVD), renal disease and other diabetes related complications. RESULTS: From the whole admissions, 6037 (17%) hospitalizations were attributed to DM (first-listed, chronic complications and GMC), 3520 (58.3%) women and 2517 (41.7%) men, 1145 (19%) were from 30-44 years old patients, 2284 (38%) from 45-59 and 2607 (43%) from 60-74. DM as first-listed diagnosis accounted for 313 (5.2%) hospitalizations, chronic complications for 2394 (39.6%) and GMC for 3330 (55.2%). CVD (5.3%) and PVD (8.7%) represented 14% of all hospitalizations in the whole population, contrasting to 34.3% (20.9% and 13.4% respectively) in hospitalizations attributed to DM. Hospitalization rates were very similar between sex, except for cardiovascular disease (25% men vs. 18% women). Admissions due to DM represent 37% out of all hospitalizations for chronic diseases (6478). They represent 28% for neurological diseases, 42% for PVD, 41% CVD and 20% for renal diseases. CONCLUSIONS: DM and its complications impose a relevant burden to private health care system in Ribeirão Preto region, especially for PVD and DCV hospitalizations.