To clarify the pathogenesis of respiratory disease induced by drug allergy, clinical features and allergic examinations were evaluated in 9 patients (10 episodes). The ten episodes were classified as a case with bronchospasm, 7 cases with PIE (pulmonary infiltration with eosinophilia) syndrome and 2 cases with IP (interstitial pneumonia) according to clinical features and chest X-ray findings. In the case of bronchospasm, serum IgE level was low and Prausnitz-Kustner reaction was negative. However, increased LTC4 and LTD4 production in peripheral leukocytes and a normal level of histamine release in whole blood induced by the causative drug were shown. All cases of PIE syndrome revealed positive DLST (drug lymphocyte stimulation test). Four of 7 cases with PIE syndrome had high levels of serum IgE. One case showed decreased serum IgE level as the pulmonary infiltrtation shadow improved. In cases of IP, positive DLST and increased lymphocytes in BAL (bronchoalveolar lavage) fluid were shown. Four cases of PIE syndrome and a case of IP underwent BAL revealing an increase of eosinophils in all cases and an increase of lymphocytes of 3/5 cases. DLST using BAL lymphocyte revealed a higher stimulation index compared to that using peripheral lymphocyte. These results suggest that non-IgE-mediated allergic reaction in bronchospasm, IgE-mediated allergic reaction in PIE syndrome, and cell-mediated allergic reaction in PIE syndrome and IP are involved in pulmonary changes induced by drug allergy.