Histamine release from basophils induced by anti-IgE was studied in 8 patients with chronic bronchitis and 50 patients with bronchial asthma by analyzing doseresponse curves. As the result, there were no significant differences in maximum percent histamine release from basophils among three groups of healthy subjects (24.7± 14.2%), patients with chronic bronchitis (27.7±22.1%) and those with bronchial asthma (28.4±17.0%). In the patients with bronchial asthma, the maximum percent histamine release was higher in accordance with higher serum IgE levels, and low maximum percent release was observed in patients with intrinsic asthma (14.1±7.2%). Study of dose-response curves of anti-IgE-induced histamine release showed that a negative slope from E(2) to E(1) was observed in both healthy subjects and patients with chronic bronchitis. The majority of asthmatics with serum IgE levels of 501IU/ml or over showed a positive slope from E(2) to E(1).