In this article, a discussion of the definition and description of brief interventions is followed by broad reviews of their effectiveness in the cigarette smoking and alcohol fields. It is then argued that brief interventions should not be justified only in terms of early intervention; that there is at present insufficient evidence to warrant the abandonment of conventional outpatient treatment for clinic attenders; and that the relative contribution of motivational and active behaviour-change components of brief interventions is an important area for research.