Of the estimated 5,000,000 mental defectives in the United States, only 150,000 are in specialized public facilities.1Many factors influence admission—the degree of deficiency, age, physical handicaps, personality, behavior, economic and sociocultural background, and interactions with family and community. Mentally deficient patients are usually classified by age, sex, diagnosis, and intelligence quotient (IQ). We reported previously on the effect of these variables upon the probability of death in and release from a hospital for the mentally deficient.2-5In another paper, patients hospitalized at an early age were contrasted with older admissions.6The sociocultural status of the families was the subject of additional investigations.6,7A more comprehensive tabulation of the characteristics of patients, their parents, and their environment is presented in this paper. It is based on information which was collected as part of a major population study at Pacific State Hospital, a California institution for mental