The nature and evolution of one preservice secondary teacher's beliefs about mathematics are described in this paper. It provides information on how the teacher's conceptions about mathematics, teaching, and learning evolved during a secondary methods course and student teaching. The teacher communicated narrow views about the nature of mathematics and the core beliefs changed very little during the study. The main evolution during the methods course was an increased awareness of reform themes. Although the teacher refined some views during student teaching, the most significant change involved the ability to elaborate beliefs with specific classroom examples. The paper also explores the relationships between espoused beliefs and teaching decisions in the context of a reformed classroom environment. Contains 12 references. (Author/AIM)