THIS STUDY on the efficacy of high dose chlorpromazine treatment in chronic schizophrenia was developed under the National Institute of Mental Health (NIMH) psychopharmacology program during 1964 and was initiated in seven collaborating public mental hospitals early in 1965. The hospitals participating in this study were Boston State Hospital, Boston; Broughton State Hospital, Morganton, NC; Dorothea Dix State Hospital, Raleigh, NC; Kentucky State Hospital, Danville, Ky; Manhattan State Hospital, New York; St. Louis State Hospital, St. Louis; and Springfield State Hospital, Sykesville, Md. These hospitals were selected to represent the entire urbanrural continum. Three hospitals admitted patients exclusively from large urban centers, two hospitals served areas which included both urban and rural communities, and two hospitals served areas which were almost exclusively rural. Background During the past 13 years, a large number of studies have been published on the use of chlorpromazine with chronic schizophrenic