The aim of this study is to explain students' ability to transfer their knowledge about mathematical series to the problems that they encounter. The data of the study were obtained by using two different tests, namely "Problem Solving Test (PST)" and "Series Character Identification Test (SCT)" which were developed by the researchers. The study was conducted to third- grade students from department of elementary school mathematics education in the 2009-2010 academic year. In view of the analysis of the data, it was observed that the students experienced no difficulty in the SCT which required procedural knowledge. They experienced difficulty in the PST which required skill to transfer their knowledge about the series to the circumstances that they encounter. According to these results, it was determined that the students experienced difficulty in transforming real life problems to series and interpreting these problems. (Contains 2 tables and 3 figures.)