Influences of IgE-mediated allergy and cigarette smoking on pathophysiology, evaluated by bronchial hyperresponsiveness and the generation of LTB4 and LTC4, of asthma were examined in 69 patients with asthma sensitive to inhalant allergens such as house dust mite and Candida albicans. 1 . Bronchial byperresponsiveness was significantly higher in previous and current smokers of asthmatics than in never-smokers. 2 . The generation of leukotrienes 84 (LTB4) and C4 (LTC4) by leucocytes was significantly larger in patients with serum IgE over 350 IU/ml than in those with serum IgE less than 150 IU/ml (LTB4 : p