This study investigated the changes in conceptions on mathematics teaching and learning of preservice BScEd teachers after 12 weeks of full time teaching practice. Written answers to open ended questions administered at the beginning and end of student teaching were triangulated with interviews. The preservice teachers exhibited more differences in conceptions on teaching than on learning mathematics. Students' age, class level, the nature of mathematical content and the need to match students' discursive skills with their achievement in written work influenced the preservice teachers' pedagogical and epistemological beliefs. The paper postulates some possible factors that influenced preservice teachers' conceptions on mathematics instruction. (Contains 1 table.)