This study was carried out to manifest risk factors related grain dust induced asthma, especially allergic and immunologic factors. Six grain workers first diagnosed as grain dust induced asthma by specific antigen bronchial asthma challenge test (cases) and 37 grain workers showed negative finding (controls) in the same firm were selected. Questionnaire survey for respiratory symptoms, interview, physical examination, PFT, methacholine bronchial hyperresponsiveness, specific challenge tests and skin prick test for four grains (grain, corn, rye and seed dust) were conducted. To evaluate the role of specific antibodies to grain dust, we detected serum specific IgE and IgG antibodies by ELISA in 43 employees. The results were summarized as follows : 1. Compared with the group having no respiratory symptoms, odds ratio of grain dust induced asthma with respiratory symptoms was 3.04 (95% CI 0.32-28.80). 2. Compared with the group having no ventilatory impairment, odds ratio of grain dust induced asthma with ventilatory impairment was 0.54 (95% CI 0.06-5.21). 3. Compared with the group showed negative skin test for general respirable antigen, odds ratio of grain dust induced asthma with atopy was 8.02 (95% CI 0.42-153.25). 4. Compared with the group showed negative finding on specific allergic skin test, odds ratio of grain dust induced asthma with positive finding was 5.88 (95% CI 0.63-55.38). 5. In immunologic test, compared with the group not increased total IgE(<160 IU/ml), odds ratio of grain dust induced asthma with increased group (> or = 160 IU/ml) was 4.78 (95% CI 0.50-44.57). 6. Compared with the group showed negative finding on specific IgE antibody, odds ratio of grain dust induced asthma with positive finding was 2.63 (95% CI 0.43-16.16). 7. Compared with the group showed normal finding on nonspecific (methacholine) bronchial hyperresponsiveness, odds ratio of grain dust induced asthma with positive finding was 76.82(95% CI 3.37 - 1566.34). Statistically significant odds ratio were fecund for specific skin test with grain, total IgE and nonspecific (methacholine) bronchial hyperreponsiveness.