The purpose of this study was to describe the characteristics of patients with bronchiolitis admitted to a paediatric intensive care unit (PICU), and to evaluate a national registry of hospitalizations (Programme de Médicalisation des Systèmes d'Information; PMSI) as a potential source of epidemiological data. Of the 49 French PICUs invited to take part in a retrospective survey of children aged <2 years who were hospitalized during the 2005-2006 epidemic season, 24 agreed to participate. Overall, 467 children were enrolled: 75% were aged <2 months, 76% had positive respiratory syncytial virus (RSV) tests, 34·9% required non-invasive ventilation, 36·6% were mechanically ventilated, and six infants died. The main neonatal characteristics were: prematurity (31·9%), respiratory disease (16·5%), congenital heart disease (6·4%), receiving mechanical ventilation (11·6%), and bronchopulmonary dysplasia at day 28 (3·8%). For bronchiolitis episode, the kappa coefficient between the survey and PMSI data was good only for mechanical ventilation (0·63) and the death rate (0·86).