Several research projects on work-related respiratory diseases have been conducted in Finland. One of the largest, "Farmers' Occupational Health Programme," was conducted by the Social Insurance Institution of Finland during 1973-1983 in cooperation with Kuopio Regional Institute of Occupational Health and the National Board of Health. The main objective of the program was to develop a model for occupational health services for farmers. As a part of the program, postal surveys were conducted in 1979 and 1982. The surveys allowed an analysis of both the prevalence and the mean annual incidence of asthma, farmer's lung, and chronic bronchitis as well as of background variables related to the diseases. More than every tenth farmer suffered from these respiratory diseases. The occurrence of chronic bronchitis (the most common disease) was, in general, related to farming types in which grain crops (including animal feeds) were handled. Chronic bronchitis was most prevalent among farmers who worked in piggeries, implying a combined effect of grain dusts, dusts of animal origin, and development of the disease. Atopy predisposed to and had an additive effect with smoking on chronic bronchitis.