Objective: To determine the frequency of later respiratory tract morbidity after respiratory syncytial virus (RSV) disease in infancy. Design: Cohort study with passive, clinic-based surveillance. Setting: Outpatient department in The Gambia. Subjects: One hundred five children admitted to the hospital with severe RSV disease (case cohort), 105 control children matched for age not admitted to the hospital during the previous RSV season (control cohort 1), and 102 control children born after the RSV season (control cohort 2). Main outcome measures: Frequencies of pneumonia, wheezing, and hospital admission with acute lower respiratory tract infection. Results: Pneumonia was more common in case children than in both control groups (adjusted incidence rate ratio [IRR, 95% CI]: 3.80 [2.73, 6.10]), as was wheezing (IRR 7.33 [3.10,17.54]), pneumonia or wheezing (IRR 3.96 [2.60, 6.04]), and admission with pneumonia or wheezing (IRR 3.40 [1.87, 6.15]). The incidence rate per 100 child-years for pneumonia in the dry season for 12-month-old children was 27 for case patients, 8.1 for control cohort 1, and 6.51 for control cohort 2. By 3 years of age, the rates had fallen to low levels in all groups. Conclusions: Pneumonia and wheezing are significantly more common in children after RSV-associated lower respiratory tract disease than in control subjects, but the incidence declines rapidly with increasing age. (J Pediatr 1999;135:683-8)