The purpose of this study was to propose and test a motivational model of persistence in science education. The model posits that science teachers' support of students' autonomy positively influences students' self-perceptions of autonomy and competence. These self-perceptions, in turn, have a positive impact on students' self-determined motivation toward science which leads to their intentions to pursue science education and eventually work in a scientific domain. This model was tested with high school students (n=728). Results from univariate analyses of variance and from structural equation modeling analyses (with LISREL) were found to support the proposed model. In addition, a direct link was obtained between perceptions of competence and intentions to pursue a science education, indicating that higher levels of perceived competence predicted higher levels of persistence intentions. The present findings support Self-Determination Theory and open the way to future research from a motivational approach in this area. (Contains 4 figures and 5 tables.)