Researchers (Ball, 2003; Ma, 1999; Schulman, 1986) have long investigated how a teacher's subject matter and pedagogical content knowledge impact on students' learning of mathematics. In an attempt to account for the relationship between teacher knowledge and student learning, this study examined four Romanian first grade teachers' knowledge about place value concepts, and the relationship between this knowledge and their classroom practice. Findings reveal a direct relationship between teachers' content and pedagogical content knowledge and their student learning of place value concepts. As such, the deeper understanding teachers had about place value concepts, the richer learning opportunities they created for their students and the better understanding their students had of place value concepts, as revealed by student test scores. (Contains 4 footnotes.)