Two cases of severe bronchial spasm in patients under general anaesthesia are presented. In the first case the bronchial spasm, according to our clinical impression, was due to histamine release following a rapid intravenous injection of 15 mg of d-tubocurarine; 100 mg of lignocaine, administered intravenously, abolished the spasm. In the second case the spasm was induced reflexly by the intubation of the trachea in a patient under thiopentone anaesthesia; 40 mg of procaine, intravenously, ended the attack. The possible mechanisms by which local anaesthetic drugs may induce relaxation of the bronchial muscle are discussed.