The aim of the study was to evaluate the effect of single and repeated fexofenadine (120 mg/day) doses on histamine-induced bronchoconstriction. Sixteen patients with mild, stabile asthma were examined. Bronchial reactivity was estimated as histamine dose (in mg/ml) causing a 20% FEV1 fall. A significant blockade of histamine H1 receptors in the airways was observed from the 1st to the 3rd day of the study. In all patients treated with fexofenadine, histamine in 16 mg/ml dose failed to induce bronchoconstriction. After another three days without fexofenadine, bronchial responsiveness returned to the initial value. The study points out that fexofenadine blocks H1 receptors in the bronchial tree.