A study was designed to evaluate the effectiveness of principals in structuring teaching teams; to assess background and personality characteristics appearing essential to successful individual and team performance; and to select personality factor scores which would predict individual and team success. Subjects were 31 teaching teams (99 teachers) from nine secondary schools in a district which had experimented with team teaching for 5 years. A group of judges (the nine principals, their deans, and five university consultants) evaluated the instructional performance of each team using a five-point rating scale; they deemed 16 teams to be performing at high levels of expectation, 15 at lower levels. They listed eight background characteristics and eight personality characteristics appearing to affect team performance. The chi square test was used to determine relationships between performance and background characteristics (only education and team experience were significant) and personality characteristics as measured by the "Sixteen Personality Factor Questionnaire." Conclusions: There are personality factors definitely related to team teaching performance (cooperation, emotional stability, aggressiveness, enthusiasm, adaptability, confidence, and experimentation) which are not easily determined through observations. Personality tests would increase the effectiveness of structuring successful teams. (JS)