To investigate the annual decline of lung function in subjects with self-reported asthma, we analyzed data from a longitudinal epidemiologic study. The Copenhagen City Heart Study. The study sample consisted of 10,952 subjects (4,824 men), 20 to 90 yr of age, randomly selected from the city of Copenhagen followed over a 5-yr period. The overall prevalence of asthma was 3.7% (n = 177) in men and 3.6% (n = 219) in women. Subjects who reported asthma at the first examination had, in general, lower values for lung function than did nonasthmatic subjects, which was also the case for subjects who developed asthma during follow-up (new asthma). The annual loss of FEV1 increased with age among both asthmatics and nonasthmatics. Multiple regression analysis showed a higher decline of FEV1 in subjects with new asthma. The excess decline was, on average, 39 ml/yr in men (p = 0.002) and 11 ml/yr in women (NS), respectively, compared with that in nonasthmatic subjects. In subjects with chronic asthma, the decline was not increased compared with that in nonasthmatic subjects. Separate analyses of lifelong nonsmokers revealed that the excess decline of FEV1 in subjects with new asthma was, on average, 33 ml/yr, whereas it was not significantly increased in subjects with chronic asthma. In conclusion, this study of a large sample from the general population showed that the rate of decline of FEV1 is increased in subjects with new asthma, whereas in subjects with chronic asthma the decline of FEV1 did not differ significantly from the decline in the nonasthmatic subjects.