Serum ECP levels were significantly higher in asthmatic patients than normal controls(p<0.0,5). Serum ECP levels were correlated with peripheral bloodeosinophil counts(p<0.01, r=0.544) and bronchial hyperresponsiveness(PC,)(p<0.01, r=-0.456) in patients with bronchial asthma. Serum ECP levels were correlated with degree of bronchial obstruction(FEV, % to predicted value, FEV1/FVC%) in total subjects, but not in asthmatic patients.