The prevalence of storage mite allergy was investigated in an epidemiological study of respiratory symptoms in farmers on Gotland, an island in the Baltic Sea. A questionnaire concerning work-related and chronic symptoms from the airways and eyes was completed by 2578 farmers. A sample of 440 farmers subsequently underwent examination comprising skin-prick tests (animal danders, pollens, moulds and house dust mite), blood sampling for RAST against four storage mites (Acarus siro, Lepidoglyphus destructor. Tyrophagus putrescentiae and Glycyphagus domesticus) and total IgE analyses. Immediate onset hypersensitivity reactions in the airways and eyes were very common among active farmers on Gotland, the prevalence being as high as 40.0%. The prevalence of atopic allergy was 15.6%. Allergy to storage mites was diagnosed, from the case history and a positive RAST to at least one of the four storage mites, in fifty-two of 440 studied farmers (12%), corresponding to a calculated prevalence of storage mite allergy in the whole farming population of Gotland of 6.2%. The corresponding prevalence among farmers with hypersensitivity symptoms was 15.4%and among those with possibly IgE-mediated symptoms it was as high as 37.8%. The present study clearly demonstrates a high prevalence of allergy to storage mites among farmers with respiratory symptoms.