to determine the frequency, complications and seasonality at which respiratory syncytial virus (RSV) infection of the lower respiratory tract causes hospitalization in infants of age 1 year or less in 6 cities of Colombia.one-year prospective multicentric observational study that included 717 patients presenting to the emergency department with respiratory symptoms in 6 cities of Colombia. Hospitalized children were tested for RSV with an immunofluorescence rapid test in nasopharyngeal secretions. Descriptive and statistical analyses of the population were conducted.the study population included 717 patients with a mean age of 3.6 months (SD 3.25), 4:3 male: female ratio and a positive RSV LRTI prevalence of 30.0% (216 infants/City, range 26.0 - 49.0%). Risk factors for RSV LRTI were found in 8.2% of the population, of which 28.8% were RSV positive. RSV positive and negative groups were compared using a two-tailed t test with 95.0%CI, p < 0.05. No statistically significant differences were found. All cities presented specific year trimesters in the occurrence of RSV LRTI.the RSV caused 1 in 3 LRTI hospitalizations in the population, with an incidence of 30.0%. This confirms a continuous circulation of RSV in Colombia varying by geographic location.