Standardized bronchial allergen provocation was performed twice (with an interval of median 14 days (range 14‐44)) in 19 extrinsic, well‐defined asthmatic patients to study the reproducibility of the bronchial response. Smoking and medications were strictly withheld prior to the provocation. Ten‐fold increasing concentrations of allergen solution 0.9 ml were inhaled by tidal volume breathing for 5 min at 10‐min intervals. The acutal dose given was expressed by the concentration of the solution used. Forced expiratory volume in the first second (FEV1) was used to determine responses, and the provocation continued until an allergen concentration (allergen PC20) was reached which caused at least 20% decrease of the post‐saline FEV1. All provocations were followed by a bronchial reaction within clinically acceptable limits. The reproducibility was high, evaluated by the Spearman rank correlation coefficient Rho = 0.90 (P<0.01). It is concluded that bronchial provocation with allergens performed as outlined in this study represents a reproducible test which can be applied in routine allergy diagnostics, and in further investigations concerning specific bronchial r