Pig farmers are susceptible to a number of occupational hazards which may lead to respiratory symptoms. Therefore, inhalation allergy to pig was examined in pig farmers, including 40 farmers with work-related respiratory symptoms and 40 farmers without these symptoms. The presence in serum of IgE specific to pig protein was examined by the histamine release test, based on passive sensitization of basophil leukocytes with the farmers' serum. This test showed pig-specific IgE in a highly selected group of pig farmers in a previous study. In the present study of nonselected farmers, no swine-specific IgE was found in their serum. The results are thus in accordance with previous studies of nonselected populations of pig farmers tested by RAST and skin prick test. It can therefore be concluded that IgE-sensitization to pig protein is not a common phenomenon in pig farmers.