The application of techniques of behaviour modification to chronic adult psychiatric in-patients has for the most part been directed towards individual patients, and to specific problems such as hoarding, eating, soiling or speech (Ayllon, 1963; Ayllon and Haughton, 1962, 1964; Ayllon and Michael, 1959; Bachrach et al., 1965; Isaacs et al., 1960; Mertens and Fuller, 1963; Kennedy, 1964; Sherman, 1965). In this country, Baker (1970, 1971) and Kassorla (1968) have reported on the use of operant conditioning in reinstating speech in mute schizophrenics. There have, however, been few British reports relating to groups of patients, for example in wards where nurses have been trained to function as ‘behavioural engineers' (Ayllon and Michael, 1959); whereas Krasner and Attowe (1968) specified no fewer than 200 institutions and individuals in the U.S.A. currently involved in token reinforcement programmes, concerned with disturbed or autistic children, delinquent adolescents and the mentally handicapped; 22 projects involved chronic adult psychiatric in-patients.