BACKGROUND: Rotavirus is a major cause of gastroenteritis in children. Knowledge of rotavirus genotypes is important for vaccination strategies. METHODS: During 2005-2006, rotavirus surveillance studies were conducted in São Paulo, Salvador, Goiânia, and Porto Alegre, Brazil. Stool samples were collected from children <5 years of age who had diarrhea and were screened by the Rotaclone Enzyme Immunoassay for the presence of rotavirus. Confirmed rotavirus-positive samples were characterized for P and G genotypes by reverse-transcriptase polymerase chain reaction. RESULTS: A total of 510 stool samples were collected. Of these, 221 (43.3%) were positive for rotavirus. Overall, G9 was the predominant G type, followed by G2, and G1; P[4] and P[8] were the predominant P types. The most frequent G/P genotype combination detected was G2P[4], followed by G9P[8], G9P[4], and G1P[8]. G2P[4] was the predominant type in Goiânia and Salvador; G9P[8] and G1P[8] were predominant in São Paulo and Porto Alegre, respectively. CONCLUSIONS: The prevalence, seasonality, and genotype distribution of rotavirus infection varied in different regions in Brazil. With immunization programs, continuous monitoring of rotavirus types is important to detect novel and emerging strains.