The purpose of this correlational study was to examine the relationship between fidelity of project-based curriculum implementation and foreign language teachers' beliefs in teaching and learning as constructivist or behaviorist. Quantitative data on teachers' beliefs was collected using a self-administered survey. Quantitative data on fidelity of project-based curriculum implementation was collected through classroom observations. The findings did not show a correlation between teachers' beliefs and fidelity of curriculum implementation. The study did reveal that only half of the teacher-participants demonstrated fidelity of implementation of the project-based constructivist curriculum and exposed an incongruence between teachers' espoused beliefs and their theory in practice. In order to increase fidelity of curriculum implementation it is recommended that appropriate high quality collaborative and sustained professional development focus on the successful implementation of project-based, constructivist curriculum and provide the opportunity for teachers to question their beliefs and reflect upon their teaching practice. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]