Research on client characteristics is reviewed. The degree of disturbance, client expectations, social and economic attributes, race, sex, intellectual variables, and the nature of the presenting problem are all shown to interact with treatment method in determining the outcome of counseling. Several specific recommendations are made: (1) Behavior therapy is recommended for use with clients of low socioeconomic status and/or concrete thinking abilities. (2) Clients with limited social assets (education, jobs, attractiveness) might profit from attention to these areas first, before their intrapsychic problems are approached. (3) Therapy dependent on a lot of client talk is inappropriate for independent males and dependent females. A more structured approach is recommended for these clients, at least at the beginning of treatment, so that they will not defect before obtaining any benefits. (4) Therapists should treat different psychological disorders with different treatments. A catalogue of disorders and treatments is recommended. (Author)