An integrated mathematics and science methods course was designed to focus on the knowledge, skills, and beliefs of teacher candidates. Teacher candidates were involved in experiences that would prompt them to consider the influence of their experiences on their beliefs, the influence of their beliefs on their instructional decisions and the impact of those decisions on their effectiveness as teachers. Three teacher candidates who exhibited high levels of reflection and who made significant changes in the ways that they thought about mathematics and the teaching/learning process were chosen for study. Two themes related to this cognitive change emerged: a more complex, sophisticated understanding of the nature of mathematics; and an increased focus on children's thinking to guide instruction. Three program components having a major impact on these students' reconceptualization were reflection on past experiences, engagement in mathematical problem-solving and opportunities to act on new beliefs. (Contains 1 figure.)