Groups were used in many studies merely to generate sufficient numbers of subjects to allow various types of interventions to be compared, rather than to examine group process variables per se. Only a limited amount of attention had been given to whether these group interaction variables (such as group discussion, sharing ideas and feelings, and mutual feedback and reinforcement) might enhance individually oriented procedures applied in a group. The 8 years since this original chapter was written have seen a significant growth in both the breadth and depth of clinical research and work in the behavioral group therapy field. This growth was documented in part in a three­ volume series on behavioral group therapy by the current editors (Upper & Ross, 1979, 1980, 1981).