This study investigates the claim that effective teacher behaviour is rooted in teacher beliefs about the nature of knowledge, learning and ability. A longitudinal design was used to obtain data on student teachers' epistemic beliefs, instructional preference and teaching competence. Results from statistical analyses show that there were significant changes in student teachers' epistemic beliefs over a four year period and these beliefs predicted the student teachers' instructional preferences. The impact of epistemic beliefs on teaching competence was mixed. Only beliefs about source of knowledge had a significant impact on teaching competence. Implications of these findings are considered. (Contains 3 tables.)