The authors apply current influential models from the motivational literature to develop the comprehensive factors influencing teaching choice (FIT-Choice) scale, to measure factors influencing the choice to teach for beginning preservice teacher education candidates. They validate the scale using 2 large cohorts (N = 488; 652) and describe the factors that teacher education candidates identified as most important in their decision to teach. Furthermore, the authors examine longitudinal relationships for participants who have now completed their teaching qualification (N = 294) to determine how entry motivations relate to exit levels of teaching engagement and professional development aspirations. The study makes several important theoretical contributions: The authors extend the values component of the expectancy-value motivational framework, go beyond high school students to examine career choices of adults, and specifically examine the domain of teaching as a career choice. The new FIT-Choice measure provides a theoretical and analytical framework to help guide future investigations in this area. Understanding teacher candidates' motivations for choosing teaching has implications for teacher education planning and curriculum design, teacher recruitment authorities, and government and intergovernmental planning and policy decisions--especially when many. (Contains 1 figure and 8 tables.)