In a study of acute respiratory disease, two collections of nasopharyngeal aspirates (NPA) were obtained from children hospitalized at the Pediatric Clinic of the University Hospital, São Paulo, in 1995 and 2000. Adenovirus was detected in 33 (8.2%) of 401 children followed. These viruses were isolated in HEp-2, HEK-293, or NCI-H292 cells and serotyped by neutralization. The genome types were determined after restriction analyses of the genomic DNA extracted from infected cells. Nineteen isolates were characterized as Human adenovirus B, genome types HAdV-3a, HAdV-7h, and HAdV-7h1; 11 as Human adenovirus C, genome types HAdV-1D10, HAdV-2D25, HAdV-5D2, and HAdV-6D3. Our findings show that species C adenoviruses present an endemic infection pattern, with co-circulation of different serotypes and genome types; no new genomic variant was observed. Species B adenoviruses showed epidemic infection patterns, with shifts in the predominant genome type. The isolates from 1995 belong to genome type 7h, or the variant 7h1, with a clear substitution of the type 7b, prevalent in São Paulo for more then 10 years. In 2000, the variant 7h1 predominated and the emergence of the type 3a was observed. Almost 10 years passed between the identification of HAdV-7h in Argentina and its detection in São Paulo. The geographic isolation of these two countries was reduced by the increase in population mobility due to growing commercial relationships.