Research Findings: In the past 20 years school districts have increasingly adopted classroom-based social and emotional development programs. The dissemination of these programs, however, has surpassed our understanding of and ability to assess factors that influence program implementation. The present study responded to this gap by developing a questionnaire that focuses on teacher perceptions of implementation support and teacher attitudes about social-emotional learning and by assessing its psychometric properties. One hundred forty-five Baltimore City Head Start preschool teachers completed the questionnaire. Factor analyses suggested 6 underlying constructs, which we termed administrative support, training, competence, program effectiveness, time constraints, and academic priority. Several of these scales predicted teacher reports of program implementation. Practice or Policy: The questionnaire holds significant promise as a tool for assessing readiness and barriers to social and emotional program implementation. (Contains 2 tables and 1 footnote.)