In this longitudinal study of a general population sample, remissions of asthma were common only during the second decade of life and were especially unusual in subjects ages 30 to 60 years on enrollment. Asthmatic subjects with severe symptoms, with reduced ventilatory function, or with a concomitant diagnosis of chronic bronchitis or emphysema on entry to the study were very unlikely to be in remission nine years later. Relapses of disease were common in subjects with a past history of asthma who were considered to be quiescent on enrollment to the study. Relapse rates tended to increase with age, at least up to the age of 70. Relapses were especially frequent among those "ex-asthmatics" who had persisting respiratory symptomatology on entry to the study.