Fluphenazine, one of the newest phenothiazine derivatives, has trifluoromethyl and piperazine groups which bring about increase in potency. In Britain it is used in doses of 1 mg. or 2 mg. daily for the relief of anxiety, but American reports indicate that the drug is also of value in psychotic illnesses (Darling, 1959; Niswander and Karacan, 1959; Taylor, 1959, 1960; Darling et al., 1960; Holt and Wright, 1960). Encouraging results were also obtained in a preliminary study conducted in Britain in a group of patients of whom most were psychotic, and daily doses of 2 or 3 mg. appeared to be effective in relieving anxiety and agitation in a considerable proportion of these cases (Gillman and Sutherland, 1961). In reviewing the human and animal pharmacology of fluphenazine, Heseltine (1961) commented on its differences from earlier drugs like chlorpromazine and triflupromazine. The increased potency of the new drug, which in many pharmacodynamic properties may be about 40 times as potent as chlorpromazine, is associated with a rapid and prolonged action, relatively little sedative activity and little or no increase in autonomic and haemodynamic effects. A trial was undertaken to investigate the effectiveness of fluphenazine in the treatment of schizophrenic patients.