The major objective in the study was to identify those background and personality characteristics of teachers which are associated with effective team performance. To add to the practicality of the findings two methods of personality assessment were examined: (a) the accuracy of the school principals in making estimates on certain personality factor dimensions in their teachers; and (b) the teacher's response to items on Cattell's Sixteen Personality Factor Questionnaire. The subjects used in the investigation were the ninety-nine teachers performing in thirty-one teaching teams in the Jefferson County, Colorado, Public Schools. Data collected on these individuals included: (1) background or biographical information; (2) two estimates on each personality factor of the teacher, as judged by the principal; (3) personality test scores; and (4) performance ratings of the judges on each teacher and the total team. [...]