THE PRESENT STUDY WAS DESIGNED TO DETERMINE WITHIN GROUP PLAY THERAPY--(1) THE COMBINATION OF EXPERIENCES WHICH PRODUCE THE GREATEST CHANGE IN BEHAVIORS AND THE EMOTIONAL STATE, AND (2) WHETHER TREATMENT INCLUDING TANGIBLE REWARDS PRODUCE MORE CHANGE THAN TREATMENT EXCLUDING THEM. THE 11 THIRD-GRADE BOYS REFERRED BY TEACHERS BECAUSE OF THEIR SHY, WITHDRAWN BEHAVIOR WERE RANDOMLY ASSIGNED TO THREE PLAY GROUPS. GROUP XA, COMPOSED OF FOUR BOYS, WAS TREATED BY THE THERAPIST (T), RECEIVING TANGIBLE REINFORCEMENTS IN THE FORM OF TOKENS FOR ASSERTIVE AND SOCIAL APPROACH BEHAVIORS. GROUP XB, COMPOSED OF FOUR BOYS, WAS SIMILARLY TREATED, EXCEPT THAT NO REINFORCEMENTS WERE GIVEN. GROUP CA, WITH THREE BOYS, SERVED AS THE CONTROL. RESULTS INDICATED THAT ALL GROUPS FAILED TO EXHIBIT CHANGE IN PRODUCTIVITY AS MEASURED BY TEACHERS'S GRADES, ANXIETY, GENERAL PSYCHOLOGICAL ADJUSTMENT, AS REPORTED BY MOTHERS. IN THE TWO REMAINING DEPENDENT VARIABLES, XA IMPROVED MORE THAN XB, AND XB IMPROVED MORE THAN CA. XA EXHIBITED INCREASED SOCIAL ADJUSTMENT AS MEASURED BY RESEARCH ASSISTANTS DURING THE THERAPY SESSIONS, AND DECREASED PROBLEM BEHAVIOR AS REPORTED BY THE MOTHERS. LIMITATIONS TO THE STUDY ARE--(1) THERE WAS ONLY ONE THERAPIST WHO ALSO SERVED AS THE SENIOR INVESTIGATOR, (2) THE VERY SMALL SAMPLE SIZE, (3) THE DIFFICULTY OF GENERALIZING FINDINGS, AND (4) THE QUESTIONABLE VALIDITY OF SUBJECTIVE MATERNAL REPORTS. (AUTHOR)