The present study investigated which aspects of group behavior and interaction are influenced more by the particular psychotherapist and patients involved than by the type of group therapy session. Taped segments from three therapists' groups, with each group attending under three controlled conditions, were rated "blind" for 37 aspects of group emotion, behavior, and interaction. The style of behavior preferred by each group therapist influenced particular patterns of group interaction and the groups' characteristic response to stress.Abstract Teaser