Humoral and cellular immune responses in bronchial asthma were examined by comparing the results of older asthmatics (group OA) with those of older healthy subjects (group OH) and of younger asthmatics (group YA). In humoral immune response, IgE-mediated immune system expressed by elevated serum IgE levels and IgE antibodies for house dust mite (HDm) and/or Candida albicans was clearly found in older asthmatics, while there was no finding showing the presence of IgE-mediated immune response in older healthy subjects. There was no significant difference in levels of serum IgG and IgA among the three groups. However, the serum IgM level was significantly lower in older asthmatics than in younger asthmatics. IgE antibodies to HDm and/or Candida albicans were more frequently found in older asthmatics compared with older healthy subjects. In contrast, IgG(4) antibodies to HDm were not different among the three groups. IgG(4) antibodies to Candida albicans were significantly higher in both older groups than in younger group. However, there was no significant difference between asthmatic and healthy subjects in the elderly. Delayed skin reaction to PPD was significantly more decreased in older asthmatics. These results show that bronchial asthma in the elderly is characterized by the presence of IgE-mediated immune response and by the changes of immune response with aging.