The longitudinal lung function data in 286 subjects from a 28 year follow-up of childhood asthma is reported. Airway obstruction in mid-adult life was present mainly in those with moderately severe asthma. Subjects who had been wheeze free for at least 3 years, even if asthma had been persistent in childhood, had normal lung function and no increased bronchial reactivity. Only two subjects, both with persistent asthma from childhood, failed to show an improvement in FEV1 of greater than 10% following inhalation of a beta-adrenergic agonist. Subjects with relatively mild asthma who had not taken inhaled steroids did not appear to be disadvantaged with respect to lung function.