Total serum IgE and IgE antibodies against ten common antigens, including Dermatophagoides farinae (D.f.), moth, ragweed, orchard grass, cryptomeria, alternaria, aspergillus, dog dander, cat dander and tetanus toxoid, were determined using the PRIST and the Sepharose-RAST, respectively, in 100 clinically non-allergic Japanese subjects and interrelations of IgE responses to these antigens were investigated. We obtained following results. The number of positive RAST antigens, to which the subjects responded, increased in parallel to their total serum IgE levels. Among ten antigens, D.f. and moth antigens contributed a great deal to the elevation of total serum IgE level as compared with other antigens. When the relationship between IgE response to D.f. and similar responses to the other nine antigens was investigated, positive RAST responses to various antigens occurred selectively in the subjects with positive RAST for D.f., and the number of positive RAST antigens to which the subjects responded increased depending upon their D.f. specific RAST levels. Such an association was not found between IgE response to moth and the other nine antigens. These findings suggest that non-specific activation of IgE-producing B cells occurs as a result of continuing stimulation by D.f.