The efficacy of nebulized hypertonic saline (HS) therapy for shortening hospital length of stay (LOS) or improving bronchiolitic symptoms remains controversial. Most studies enrolled small numbers of subjects and did not consider the role of respiratory syncytial virus (RSV), the most common cause of acute bronchiolitis. Our aim was to evaluate the efficacy and safety of nebulized HS therapy for acute bronchiolitis due to RSV in moderately ill hospitalized infants.