This article reports three studies in which a scale for assessing teachers' beliefs about professional-development initiatives was developed and its scores evaluated for reliability and validity. Results indicated that the Teachers' Attitudes About Professional Development (TAP) scale produced scores with high reliability, a stable one-factor structure, and satisfactory construct and discriminant validity (relative to measures of need for social approval, need for cognition, authoritarianism, and teacher self-efficacy). The studies support the theoretical and practical utility of the construct and measure of teachers' beliefs about professional development.