Prior to the behavior therapy sessions, the parents of each child were seen in interviews aimed at obtaining descriptions of the behavior which created problems at home and/or at school. All mother-child cases were seen separately for approximately twenty-minute sessions, held once or twice weekly in the playroom. The mother and her child were always the sole occupants of the playroom. Most psychotherapists assume that a child's parents compose the most influential part of his natural environment. It is likely, from a learning theory viewpoint, that their behaviors serve a large variety of stimulus functions, controlling both the respondent and operant behaviors of their children. Techniques of parent-child psychotherapy have been investigated by several researchers. However, the procedures used in these studies did not permit assessment of variables which were maintaining the children's deviant behavior, nor did they permit analyses of those variables which were responsible for changing the deviant behavior.