Infants with viral bronchiolitis are currently treated with oxygen therapy if oxygen saturation is low. In earlier observational clinical studies, the use of high flow nasal cannulae therapy in infants with bronchiolitis has been associated with a decreased rate of intubation and intensive care. This study is a randomized controlled trial in five pediatric university hospitals in Finland comparing high flow nasal cannulae therapy to usual oxygen therapy in infants with bronchiolitis.