A secondary school mathematics teacher and mathematics education researcher engaged in a collaborative professional development experience that focused the teacher's reflection on videotapes of his instruction. The purpose was to document and explore the teacher's experiences with respect to his reflections and classroom practice while trying to create inquiry-based mathematical discourse. Data included videotaped classroom observations, audiotaped interviews, and audiotaped focused reflection sessions. Analysis of the data revealed that over the course of the semester-long collaboration the teacher exhibited, at various times, four different reflective states ("explain but not question", "question but not explain", "question and explore", and "exploring"). The identification of these reflective states suggests a more complex relationship between reflection and changing teachers' practice than previously thought. The results of this article suggest that the interaction of teachers' reflective activities and reflective states contribute to various kinds of teacher change in the classroom. (Contains 3 figures.)