The reliability and validity of the Myself as a Teacher Scale (MTS), developed to assess the self-concept of teachers, were studied. Materials developed by David P. Butts and Robert Howe were used to construct a 62-item Likert-type scale asking individuals to rate themselves on certain criteria. After a pilot study with 92 preservice teachers and item analyses, the number of items was reduced to 32. Initial internal reliability was derived from a study of these 32 items. A second group of 42 student teachers was tested, and a reliability coefficient of 0.92 was achieved. A retest with these students found a test-retest reliability coefficient of 0.89. The internal consistency of the MTS was evaluated using 426 student teachers for an alpha coefficient of 0.96. Thirty-two preservice teachers were administered the MTS and the Tennessee Self Concept Scale for a modest correlation, indicating concurrent validity. Predictive validity was examined in studies of the classroom performance of student teachers and teacher morale of 35 first-year teachers. Factor analysis through principal component analysis of responses of 422 preservice and inservice teachers demonstrated construct validity. One major dimension of behavior, an overall measure of self-concept as a teacher, was identified. The MTS appeared to be an effective measure. Factor loadings are listed in table form. (SLD)