Twenty-two (42 per cent) out of 52 patients admitted with severe bronchiolitis to our Paediatric Intensive Care Unit required ventilation. Risk factors associated with ventilation included a younger mean age, female sex, low birthweight, failure to thrive and the presence of an underlying illness. Ventilated patients were also more likely to have a higher respiratory distress assessment index (RDAI) score, pneumonic infiltration on chest X-ray, lower serum sodium and a positive respiratory syncytial virus isolation in the tracheal secretion.