This paper reports on a portion of a research study that examined the development of 43 preservice elementary school teachers' conceptual understanding of place value, and highlights the experiences of one middle-performing preservice teacher. After participating in a research-based constructivist unit of instruction in place value, the findings showed that the preservice teachers demonstrated a statistically significant change in place value understanding. Common emergent mathematical qualities and qualities of disposition were identified in the qualitative analyses. These data provided insight into this preservice teacher's thinking strategies. [For the complete proceedings, see ED597799.]