In the literature, it has been reported that primary school teachers have not grasped enough knowledge of basic science concepts, and have held misconceptions about them. The purpose of this study is to determine prospective science teachers' levels of understanding and misconceptions about some basic chemical concepts. 200 student teachers enrolled in the primary teacher-training program, 100 of them were at the first year; the others were at the final year, participated in this study. Data was collected from a test consisting of 25 items and individual interviews conducted with 12 students to support the findings. The test scores obtained from both ffrsiyear students and final-year students were compared by using a t-test technique. The results from this study showed that the prospective science teachers have not got sufficient understanding and have held a number of misconceptions related to the concepts. Also, it was found that the prospective science teachers at the first year are more successful than those at the final year. Based on the results, some suggestions were made.