The release mechanism of chemical mediators from basophils and mast cells was discussed when these cells were stimulated by different antigens and anti-IgE. 1. Ca(2+) influx into mast cells increased after stimulation by antigen. The increased Ca(2+) uptake by mast cells was inhibited by antiallergic agents, disodium cromoglycate (DSCG) and tranilast, and calcium antagonists, nifedipine and nicardipine. 2. The dose-response curve of histamine release by antigen was different from that by anti-IgE. The maximum release of histamine by house dust was, however, similar to that by anti-IgE. House dust- and anti-IgE-induced release of histamine increased with higher- serum IgE levels. On the contrary, the release of histamine by Candida albicans was not releated to serum IgE levels, and the release by C. albicans did not parallel therelease by anti-IgE.