To analyze the pathophysiological changes ot the airways in emphysema, bronchial responsiveness and the generation of leukotrienes B4 (LTB4) and C4 (LTC4) by peripheral leucocytes were examined in 22 patients with emphysema. The subjects were divided into two groups according to the presence or absence of IgE antibodies against inhalant allergens; RAST positive group and RAST negative group. 1. Smoking history, mean CT number and mean maximum % low attenuation area (% LAA) <-950HU of the lung on high resolution computed tomography (HRCT), and DLco value suggested that there were emphysematous changes of the lung in all subjects. However, these findings were not different between the two groups. 2. The level of serum IgE was significantly higher in RAST positive group than in RAST negative group. 3. The mean % increase in FEV1.0 after inhalation of β-agonists was higher in RAST positive group than in RAST negative group. The % increase more than 15% was found in 4 of the 9 subjects (44.4%) in RAST positive group and 2 of the 12 (16.7%) in RAST negative group. 4. The generation of LTC4 by leucocytes was significantly higher in RAST positive group than in RAST negative group (p<0.01). The generation of LTB4 was not significantly different between the two groups. The results suggest that IgE-mediated allergy participates in the bronchial responsiveness of patients with emphysema.