In order to compare the prevalences of common allergic symptoms identical postal questionnaires were sent to all farmers of a rural municipality in eastern Finland and to a sample of similar size in the adjacent industrialized urban municipality. To investigate the validity of the survey random subsamples of each study group participated in health examinations. In both the rural and urban populations subjects most frequently suffered from allergic rhinitis, 26.7% and 28.8%, respectively of the two populations. The proportions of individuals with any one of the five allergic symptoms recorded did not differ significantly in the two populations. Asthma was somewhat more frequent among the urban than among the rural population. The difference was not statistically significant, however, and could be due to the difference in smoking habits. The factors reported to provoke allergic symptoms were significantly different in the two groups. In the rural population the provoking factors were mostly work-related, whereas in the urban population these factors were related to living conditions.