HLA-DR and ICAM-I molecules play an important role in cellular interactions, and their expression can be induced by inflammatory stimuli. We evaluated the spontaneous expression of HLA-DR and ICAM-1 on epithelial cells obtained by bronchial brushing from 27 asthmatic patients, 10 chronic bronchitis (CB) patients, and 19 normal subjects. In all cases > 90% pure epithelial cells were obtained. HLA-DR and ICAM-1 were characterized using monoclonal antibodies and revealed by immunocytochemistry (APAAP technique). In asthma, the percentage of cells expressing HLA-DR and ICAM-1 was significantly increased by comparison with normal values (p < 0.001) and GB (p < 0.001; HLA-DR; p < 0.003; ICAM-1) and was correlated with the clinical score of Aas (p < 0.001, HLA-DR; p < 0.001, ICAM-1) and the FEV1 (p < 0.001, HLA-DR; p < 0.002; ICAM-1). In CB, expression of both markers was slightly but significantly increased by comparison with normal subjects and was correlated with FEV1 (p < 0.02, HLA-DR; p < 0.03, ICAM-1). In addition, the expression of HLA-DR and ICAM-1 was significantly correlated. This study suggests that epithelial cells are in an activated state in asthma and that the extent of expression of these markers may be specific to asthma, not a general feature of chronic inflammation.