This paper discusses the role of mathematics teachers' beliefs and their impact on curriculum reform. It is argued that teachers' beliefs about the teaching and learning mathematics are critical in determining the pace of curriculum reform. Educational change is a complex process in which teachers hold strong beliefs about the quality and the process of innovation. Curriculum implementation may only occur through sufferance as many teachers are suspicious of reform in mathematics education given its equivocal success over the past decades. It is not surprising then that many teachers, when they come to enact the curriculum in their classes, rely more on their own beliefs than on current trends in pedagogy. These beliefs, conservative as they might be, have their own rationality in the practical and daily nature of the teaching profession, and in the compelling influence of educational systems from which these teachers are paradoxically the social product. The literature indicates that many of these teachers hold behaviourist beliefs, a fact that has strong implications for the success of constructivistoriented curriculum reform. In general, studies of teachers' pedagogical beliefs reveal the extreme complexity of bringing about educational change, and largely explains the failure of many past reform endeavours.