THROUGHOUT its history psychiatry has been faced with the therapeutic problem of controlling acute and chronic states of psychomotor excitement. Much has been achieved with the advent of systematic pharmacological sedation. More recently the introduction of electroconvulsive treatment has augmented our capacity to handle successfully most of the excited states refractory to sedation by drugs. There remain, however, a number of cases in which one meets particular difficulty in controlling excitement either because of undesirable side-effects of the treatment itself or because of the patient's persistent tendency to relapse. It is the purpose of this article to report on our experiences with a new drug which seems to possess specific properties for the psychiatric management of excited states. The first clinical investigations with this drug were carried out and published in France,* where it is known as Largactil,† or 4560 R. P. It is known by the same name in