This study investigated the symptoms, medical and occupational history of 424 workers of 5 reactive dye Industries in the Inchon area in Korea. The study was performed on March 6 and July 19, 1989. The tests applied to the subjects were : serum total IgE, specific IgE, skin prick test with 7 inhalatory antigens, pulmonary function test, chest X-ray, methacholine test, and bronchoprovocation test. The workers were classified according to these tests into 4 groups (healthy, realtively healthy, need careful medical observation, and occupational asthma), and were compared in terms of the group characteristics and the symptom prevalence. The prevalece of occupational asthma of workers in reactive dye was 5.9% Significant differences were observed among the 4 groups. The groups were significantly different in the variables of sex and duration of smoking among their general characteristics ; and dyspnea, wheezing, chest pain, cough, nasal symptoms and sore throat among symptoms ; asthma, bronchitis, and other respiratory diseases with respect to their past medical history. This study suggests that we should pay special attention to the workers exposed to the risk of occupational asthma.