SummaryPeripheral blood basophils of thirty‐eight patients with bronchial asthma were examined for their reactivity to anti‐IgE and anti‐IgG antisera. Basophils of patients with serum IgE levels of more than 1001 i.u./ml reacted strongly to anti‐IgE. Basophils of patients with serum IgE levels of less than 100 i.u./ml had a tendency to react more strongly to anti‐IgG. An index (basophil ratio) was devised to compare the patient basophil reactivity to anti‐IgE and anti‐IgG. This basophil ratio was lower (IgE dominant) in the atopic cases which usually exhibited a high serum IgE level. Most cases with low serum IgE exhibited a high basophil ratio (IgG dominant). The basophils of seven intractable patients reacted more strongly to anti‐IgG than to anti‐IgE regardless of th