The effect on growth of asthma has been documented in a prospective study from age 7 to 21 years in a randomly selected group of 342 subjects. These subjects covered the whole spectrum of childhood wheezing. Growth suppression was first noted at 10 years of age in the more severely affected groups and was most marked at 14 years of age. By 21 years of age, all groups had achieved a height and weight not significantly different from control subjects. Growth delay occurred in children with more persistent asthma even if they had never received oral corticosteroid therapy but growth was more delayed in those receiving oral steroids. The effect of steroids was most significant in those with frequent episodic asthma whose asthma alone was probably not sufficiently severe to retard growth.