Summaries of arguments given in the literature both for and against the use of verbal-traditional psychotherapy with mentally retarded individuals is presented. Much research examines process variables in therapy as an approach. Feedback variables are crucial. Results of a research study in which therapy groups composed of mentally retarded adults underwent manipulations designed to affect delivery of feedback within the group are reported. Therapist style, race, and time, but not sex, affected feedback. Feedback may increase self-reinforcement and less reliance on the opinions of other people. (Author/BEF)