It has been noted that, in the practice of medicine, words have a profound effect on the conceptualization of patients' needs, the planning of services and the evaluation of programmes and systems of care (Robb-Smith, 1978). The field of psychiatry is no exception. In fact, the words used to formulate mental health policy and promote service planning in the USA often have imprecise referents and frequently reflect a vagueness of concept that may be harmful to the care of patients (Hardin, 1957; Campbell, 1981; Bachrach, 1985, 1988b,c, 1994b; Talbott, 1985; Fink, 1988). This has, at times, caused serious problems for the most severely mentally ill individuals; and it extends to those within this population who, in addition to suffering from major mental illnesses, are also homeless.

Following Hardin's (1957) advice that ‘language should periodically be put on trial’, this chapter discusses some semantic issues that affect our concepts of treatment for, and our delivery of services to, these vulnerable individuals. Primary attention is given to those problems that interfere with our efforts to delimit the mentally ill homeless population and to provide services that respond to its unique requirements. Although the major focus here is on service development within the USA, many of the derivative lessons are applicable to other countries where, with the implementation of deinstitutionalization policy, mentally ill homeless people are becoming increasingly visible (Schmidt, 1992).

The meaning of homelessness

The word ‘homeless’ is often used as if there is agreement about its meaning, when, in fact, it refers to a variety of events (Bachrach, 1992; US General Accounting Office, 1992; and see Chapter 3).