Objective　To investigate the role of endothelin(ET) in the pathogenesis of asthma and analyze the relationship between level of endothelin in induced sputum and pulmonary function:forced expiratory volume/forced vital capacity(FEV1/FVc).Methods　Induced sputum was obtained by inhaling 5% saline.Endothelin level in induced sputum obtained from 25 patients with mild or moederate attacking asthma(Group Ⅰ),26 patients with stable asthma(Group Ⅱ) and 30 healthy controls(Group Ⅲ) were measured by radioimmunoassay.Results　⑴FEV1/FVC in Group Ⅱ was higher than those in Group Ⅰ(P＜0.01),and lower than those in Group Ⅲ(P＜0.01),respectively.⑵The number of all inflammatory cells and macrophages in induced sputum from both the Group Ⅰ and Group Ⅱ were higher than those from the Group Ⅲ(P＜0.01)，respectively.⑶The level of ET in induced sputum from Group Ⅰ was higher than those from both Group Ⅱ and Group Ⅲ(P＜0.01)，respectively.⑷The level of ET in induced sputum from Group Ⅰ was negatively correlated with FEV1/FVC and oxygen partial pressure(PaO2),and positively correlated with the number of macrophages.Conclusions　There is non-specific chronic airway inflammation in patients with asthma.Endothelin may be involved in the pathological process of asthma,especially in the airway inflammation and its remodeling.The level of ET in induced sputum can reflect the level of ET in airway.