We tested the hypothesis that serum IgE concentrations may be influenced by the severity of respiratory symptoms, impairment of pulmonary functions, and smoking history in elderly patients with bronchial asthma and/or chronic obstructive pulmonary disease (COPD). A total of 325 elderly outpatients aged over 65 years were enrolled in the study: 112 (22 men, 90 women) with bronchial asthma (BA), 135 (118 men, 17 women) with COPD, and 78 (56 men, 22 women) with both COPD and asthma (COPD/BA). The mean ages for the 3 groups were 74.3,76.0 and 76.6 years, respectively; the age differential was not significant. As a group, the male subjects displayed higher serum IgE concentrations than the female subjects. Also, ex-smokers and current smokers showed higher serum IgE concentrations than patients who had never smoked, and patients in the BA group had higher serum IgE concentrations than those in the COPD or COPD/BA groups. Although serum IgE concentrations were increased in BA patients with decreased FEV_1.0 levels, the reverse was observed in the COPD patients. Peripheral blood eosinophil counts for men and women were higher in the BA group than in the COPD group. A positive correlation between serum IgE concentration and eosinophil count was observed in the BA group. Although bronchial asthma and COPD in the elderly have been considered to be pathologically similar, the findings of our study suggested they are probably differerent in terms of serum IgE concentration, pulmonary function, and smoking history.