<b>Objective:</b> The aim of the study was to determine the impact of respiratory syncytial virus (RSV) and the role of the protection afforded by palivizumab for acute lower respiratory infections (ALRIs) in infants. <b>Methods:</b> In a prospective cohort study, we investigated the impact of RSV on disease severity in infants hospitalized with ALRI and the level of protection afforded by palivizumab for high-risk infants (preterm infants &lt;36 weeks) in a tertiary hospital in Bogotá, Colombia during a 14-month period (2013-4). <b>Results:</b> Of a total of 240 infants with a diagnosis of ALRI, 188 (78.3%) were term babies and 52 (21.7%) had a preterm history. Out the total of 107 (44.6%) infants who were positive for RSV, 89 (47.3%) were born at term and 18 (34.7%) had a history of having been born preterm. 12 (23.1%) of the 52 infants born &lt;36 weeks were immunized with palivizumab. Out of the total of 240 infants, 223 (92%) were hospitalized during the first six months of follow-up, with a median length of stay (LOS) of 5.7 days (IQR: 2.0-8.0). There were no significant differences between patients with positive and negative RSV ARLI in terms of pediatric intensive care unit admission, but a significant difference was found in the necessity of ventilatory support (13.1% vs. 5.2%, p &lt;0.03) in the RSV positive subgroup. When LOS was compared between those having a history of high-risk preterm and infants born at term, there was also a significant difference between groups (12.3 vs. 7.9 days, p&lt;0.001). No related deaths were reported. <b>Conclusions:</b> Infants with RSV had longer hospitalization stays and need for ventilatory support.