OBJECTIVE:: To investigate the correlation between respiratory syncytial viral load and length of hospitalization in infants with acute wheezing episodes. METHODS:: This was a two-year, cross-sectional study of infants </= 12 months of age with bronchiolitis at the time of admission to a tertiary hospital. For the identification of respiratory viruses, nasopharyngeal secretions were collected. Samples were analyzed (throughout the study period) by direct immunofluorescence and (in the second year of the study) by quantitative real-time PCR. We screened for three human viruses: rhinovirus, respiratory syncytial virus, and metapneumovirus. RESULTS:: Of 110 samples evaluated by direct immunofluorescence, 56 (50.9%) were positive for a single virus, and 16 (14.5%) were positive for two or more viruses. Among those 72 samples, the most prevalent virus was respiratory syncytial virus, followed by influenza. Of 56 samples evaluated by quantitative real-time PCR, 24 (42.8%) were positive for a single virus, and 1 (1.7%) was positive for two viruses. Among those 25 samples, the most prevalent virus was again respiratory syncytial virus, followed by human rhinovirus. Coinfection did not influence the length of the hospital stay or other outcome s. In addition, there was no association between respiratory syncytial virus load and the length of hospitalization. CONCLUSIONS:: Neither coinfection nor respiratory syncytial viral load appears to influence the outcomes of acute bronchiolitis in infants. OBJETIVO:: Investigar a correlacao entre a carga viral do virus sincicial respiratorio e o tempo de internacao hospitalar em lactentes com episodios de sibilancia aguda. METODOS:: Este foi um estudo transversal de dois anos envolvendo lactentes de ate 12 meses de idade com bronquiolite no momento da internacao em um hospital terciario. Para a identificacao dos virus respiratorios foram coletadas secrecoes nasofaringeas. As amostras foram analisadas (por todo o periodo do estudo) por imunofluorescencia direta e (no segundo ano do estudo) por PCR quantitativa em tempo real para tres virus humanos (rinovirus, virus sincicial respiratorio e metapneumovirus). RESULTADOS:: Das 110 amostras avaliadas por imunofluorescencia direta, 56 (50,9%) foram positivas para um unico virus, e 16 (14,5%) foram positivas para dois ou mais virus. Nessas 72 amostras, o virus mais prevalente foi o virus sincicial respiratorio, seguido por influenza. Das 56 amostras avaliadas por PCR quantitativa em tempo real, 24 (42,8%) foram positivas para um unico virus, e 1 (1,7%) foi positiva para dois virus. Nessas 25 amostras, o virus mais prevalente foi o virus sincicial respiratorio, seguido por rinovirus humano. A coinfeccao nao influenciou o tempo de internacao ou outros desfechos. Alem disso, nao houve associacao entre a carga viral de virus sincicial respiratorio e o tempo de internacao. CONCLUSOES:: A coinfeccao e a carga viral do virus sincicial respiratorio nao parecem influenciar os desfechos em lactentes com bronquiolite aguda.