A study of 343 urban adult outpatients with a history of bronchial asthma was initiated in 1981. Asthma was verified by a reversibility in airflow obstruction of at least 0.5 1 in forced expiratory volume (FEV1) (70%). The rest of the 343 patients was included because of diurnal variations of at least 100 l/min in peak expiratory flow (PEF) (22%), or because of a characteristic history of asthma (8%). In 1988, a follow-up study was performed. Two hundred-fourteen patients replied (80%), 100 women and 114 men. Fifty-four did not respond, but were known to be alive. Twenty-one had emigrated; of these, the fate of five was unknown. The mortality rate was significantly raised among the men (Standard mortality rate (SMR) = 1.55). In 19%, the cause of death was pulmonary. Seventeen percent were found dead. In these, no cause of death was obvious, and they may have died from an exacerbation of their pulmonary disease. One hundred and forty-four had non-allergic and 69 allergic asthma verified retrospectively by positive skin prick test in 1988. One was not tested and not classified. Seventy-five percent of the whole group were smokers. An annual decline of approximately 90 ml per year in FEV1 was found in both groups and was only partially explained by smoking and ageing. The remaining observed decline in lung function may be caused by asthma. Reversibility of 0.5 l in FEV1 was only maintained in the allergic group.(ABSTRACT TRUNCATED AT 250 WORDS)