The authors gave 1,223 courses of antidepressant medication, and in 692 courses MAO inhibitors were used.Prior to Sept. 7, 1963, 8.4% of patients receiving MAO inhibitors experienced acute hypertensive crises featured by intense occipital headache and palpitation. After Sept. 7, 1963, patients receiving MAO inhibitors were advised not to eat cheese and the incidence of acute reactions fell to 3.3%. Of the 8 reactions in the latter series, 5 followed the ingestion of cheese, despite our warning, 2 followed the taking of cream in fairly large quantity and one occurred immediately after drinking 17 oz. of draught beer on an empty stomach after sunbathing.The highest incidence of these reactions occurred with tranylcypromine, but nevertheless this drug is being used more frequently than any other MAO inhibitor and is regarded as indispensible in the treatment of depressive illness.Acute vascular crises, when they occur, are immediately relieved with intravenous phentolamine, but where the associated cervical muscular spasm has caused impaction of apophyseal joints neck manipulation has been required. Methoxybenzamine hydrochloride also appears effective in treating these reactions.It is suggested that when an MAO inhibitor is dispensed to a patient, a label be attached to the container advising him against taking cheese, cream or alcohol, and warning his physician against giving powerful narcotic drugs, or agents related to amphetamine.