The effect of disodium cromoglycate, thiazinamium and prednisone on immediate and late type allergic bronchial reactions was studied in four patients with biphasic bronchial obstruction due to inhalation of Bacillus subtilis enzymes. The immediate reaction (type 1 allergy) was not influenced by any of these drugs. Disodium cromoglycate seemed to ameliorate the late reaction, which was very much depressed by prednisone. Thiazinamium, an antihistamine drug, did not alter the immediate nor the late phase of the reaction. The data suggest that the pathogenetical mechanism involved in Bacillus subtilis allergy may differ from that initiating bronchial reactions to pollen or house dust.