BACKGROUND AND AIMS: Asthma risk is increased after bronchiolitis in infancy. Recent studies have suggested that the risk may be dependent on the causative virus. The aim of the study was to evaluate the asthma risk in adolescence in subjects hospitalized for rhinovirus or respiratory syncytial virus (RSV) bronchiolitis in infancy. SUBJECTS AND METHODS: At the median age of 16.5 years, a questionnaire was sent to 96 study subjects hospitalized for bronchiolitis at <24 months of age and since then prospectively followed-up. Sixty-seven (70%) returned the fulfilled questionnaire. RSV and rhinovirus etiology of bronchiolitis had been studied in serum and respiratory samples obtained on admission in infancy. The occurrence of asthma was compared between former bronchiolitis patients and population controls recruited for this study in adolescence. RESULTS: Doctor-diagnosed asthma was present in 30% of former bronchiolitis patients and in 5% of controls (OR 7.9, 95% CI 3.3-19.3). The respective figures for self-reported asthma were 64% and 11% (OR 14.7, 95% CI 7.2-30.0). Self-reported asthma was more common in the former rhinovirus than RSV patients (83.3% vs. 47.6%, P = 0.023, mixed infections included; 81.3% vs. 50%, P = 0.067, mixed infections excluded). CONCLUSIONS: Patients hospitalized for RSV and rhinovirus bronchiolitis at <24 months of age had an increased asthma risk at 15-18 years of age compared with population controls. Within the former bronchiolitis group, the risk of self-reported asthma was higher after non-RSV versus RSV and after rhinovirus versus non-rhinovirus bronchiolitis.