Patients presenting to the Emergency Room (ER) or out-patient department with a diagnosis of moderately severe bronchiolitis (as defined by inclusion/exclusion criteria below) will be approached for entry into the study. After the initial routine assessment by the ER medical and nursing staff, informed consent will be obtained and the infant will be randomized to receive treatment in a double-blinded fashion with 4 ml of nebulized study solution containing 1 mg salbutamol (bronchodilator) plus either 3% hypertonic saline (HS, study group) or 0.9% saline (NS, control group) every 20 minutes for a total of 3 doses. After an observation period of 1 hour following the last dose, the infant will be reassessed by the attending physician in the ER for disposition (admit, discharge home, remain in ER for further treatment) at which point the infant's active involvement in the study will end. All subsequent therapy, if needed, will be at the sole discretion of the attending physician. The family of each recruited subject will be contacted by phone 7 days later to assess resolution of symptoms or the presence of any unexpected adverse effects.