Background: Human metapneumovirus (HMPV) is a paramyxovirus associated with respiratory illness. The genotypes of HMPV isolates in Brazil have not been well characterized. Objectives: To investigate the presence of HMPV in clinical samples collected from pediatric patients of two university hospitals in the region of Campinas (Sao Paulo, Brazil) and to genotype them by partial sequencing of the HMPV F gene. Study design: Nasopharyngeal aspirates were collected from children hospitalized between April and September, 2004 because of acute respiratory infections (ARI). Results: We identified HMPV in 8 of 142 (5.6%) clinical samples. We determined through phylogenetic analysis that HMPV isolates in Campinas during the study were clustered within subgroup B genotype 1. Two of the isolates analyzed showed significant differences from previously isolated B1 viruses, when compared to HMPV isolated in South Africa and Canada, and clustered in a separate branch within this genotype. Conclusions: In 2004 in our geographic region all HMPV isolates from pediatric patients were in the B1 HMPV genetic group, with two variant isolates.