The practice of psychiatry overlaps appreciably that of the other branches of Medicine. A high incidence of psychiatric illness has been found in out-patients attending medical and surgical clinics (Shepherd, Davies and Culpan, 1960; and Davies, 1964), and among in-patients in general medical and surgical wards (Meyer and Mendelson, 1960; Fleminger and Mallett, 1962; Eilenberg, 1965; Granville-Grossman, 1967). Other studies have shown an appreciable incidence of physical illness in out-patients attending psychiatric clinics (Davies, 1965), in psychiatric in-patients in a teaching hospital (Marshall, 1949; and Herridge, 1960), and in patients with mental disturbance attending general practitioners (Shepherd, Cooper, Brown and Kalton, 1964, 1966). The extent to which ordinary psychiatric in-patient practice involves dealing with non-psychiatric problems does not appear to have been extensively studied, although Davies, D. W. (1964) has indicated the presence of considerable physical morbidity within a psychiatric hospital population. We here describe an investigation into the incidence of physical morbidity among in-patients admitted to a general hospital psychiatric unit with a total responsibility to a catchment area population of 90,000, and into some of the factors affecting this incidence.