Objective To observe the side-effect of histamine and methacholine induced bronchial hyperresponsiveness. Methods Histamine and methacholine induced bronchial hyperresponsiveness was provoked in 60 cases of asthma patients of stable stage (normal pulmonary function) and pulmonary function meter (JAEGER) was used. Results ①Sixty cases of mild asthma patients were conducted histamine or methacholine inhalation challenge to assess airway hyperresponsiveness. Both histamine and methacholine challenge were positive, which support the existence of airway hyperresponsiveness. ②The side effect of histamine was significantly more severe than methacholin,the extent of side-effect increase with the concentration and inhalation time. Conclusions Methacholine should be the first choice for provocation test and histamine should not be used or used carefully.