The purpose of this study was to examine preservice mathematics teachers' knowledge about common (mis)conceptions and difficulties of elementary students. In addition, it Was aimed to investigate preservice teachers' knowledge about the possible sources of these misconception/difficulties, and their suggested strategies to overcome those difficulties. Data was collected from senior preservice elementary mathematics teachers enrolled in a teacher education program at a public university at the end of the spring semester of 2004-2005. Qualitative case study design was used to collect the data. Results revealed that preservice teachers' knowledge on difficulties that elementary students might have could be grouped under four headings. In addition, preservice teachers suggested various strategies that can be used to overcome students' difficulties on division of fractions. Research study revealed the importance of content-pedagogy rich courses on preservice teachers' knowledge related to students' understanding of mathematics concepts.