GROUP FUNCTIONING AND ACTIVITIES WERE STUDIED IN TWO CONTEXTS, THE LABORATORY AND THE REGULAR SCHOOL CLASSROOM. THE LABORATORY STUDY INVOLVED SMALL GROUP PROBLEM-SOLVING IN ARITHMETIC AND IN SOCIAL STUDIES. STUDIES CONSISTED OF GROUP PERFORMANCE, THE RELATIONSHIP OF THE HIGH ABILITY STUDENTS TO GROUP PERFORMANCE, THE RELATIVE IMPORTANCE OF GROUP-PERCEIVED STATUS OF THE HIGH ABILITY MEMBER, THE STATUS IMPROVEMENT OF AN ORIGINALLY UNRECOGNIZED HIGH ABILITY MEMBER, SATISFACTION OR EFFICIENCY OF GROUP ACTIVITY, THE RELATIONSHIP OF INDIVIDUAL NEEDS AND ROLES TO GROUP EFFECTIVENESS, AND THE RELATIVE IMPORTANCE OF SOCIOECONOMIC STATUS TO GROUP EFFECTIVENESS. THE CLASSROOM STUDY WAS DESCRIBED AS AN EX POST FACTO EXPERIMENT, THAT IS, THE EXPERIMENTER ARRIVED ON THE SCENE AFTER CONDITIONS HAD TAKEN PLACE AND EFFECTS HAD OCCURRED, PROCEEDING FROM EFFECT TO CAUSE. MEASURES FOR SUCH INDEPENDENT VARIABLES AS TEACHER LEADER BEHAVIOR, TEACHER INFLUENCED AND ATTRIBUTED POWER, STUDENT ABILITY AND NEEDS FOR ACHIEVEMENT, AND STUDENT AFFILIATION AND POWER WERE ENTERED INTO MULTIPLE CORRELATION ANALYSES TO DETERMINE THE OVERALL PREDICTION OF THE DEPENDENT VARIABLES (EFFICIENCY AND EFFECTIVENESS) FROM THE INDEPENDENTS. THESE TWO PROJECTS WERE FUSED INTO ONE PROGRAM BECAUSE OF SIMILARITIES OF VARIABLES UNDER INVESTIGATION. THE RESULTS OF BOTH WERE CONCEPTUALIZED INTO FUNCTIONAL RESEARCH DIMENSIONS. (JH)