OBJECTIVE: To study the epidemiology of rotavirus and estimate rotavirus-associated morbidity and mortality in children < 5 years of age in Brazil in 2004 before introducing the rotavirus vaccine in Brazil's National Immunization Program (Programa Nacional de Imunizações, PNI). METHODS: To estimate rotavirus morbidity, published studies (1999-2006) addressing incidence of acute diarrhea among children < 5 years of age and frequency of rotavirus infection among children with diarrhea in Brazil were reviewed. Diarrhea episodes were divided into three categories of severity by level of care: mild cases requiring only home-based care; moderate cases requiring a visit to an outpatient healthcare facility; and severe cases requiring hospitalization. To estimate rotavirus mortality, information on the number of registered deaths from diarrhea in children < 5 years of age was obtained from the Mortality Information System (Sistema de Informação sobre Mortalidade, SIM) of Brazil's public healthcare system (Sistema Único de Saúde, SUS) and the proportion of deaths due to rotavirus was calculated. RESULTS: Rotavirus infections were estimated to cause 3 525 053 episodes of diarrhea, 655 853 visits to outpatient healthcare facilities, 92 453 hospitalizations, and 850 deaths of children < 5 years of age each year in Brazil. CONCLUSION: Rotavirus infections are an important cause of child morbidity and mortality in Brazil.