The purpose of the present study was to investigate the effect of conceptual change text oriented instruction compared to traditional instruction on 10th grade students' understanding of reaction rate concepts. 45 students from two classes of the same teacher in a public high school participated in this study. Students in the experimental group were instructed by conceptual change text oriented instruction while students in the control group were instructed by traditional instruction. The results indicated that conceptual change text oriented instruction was more effective than traditional instruction on students' understanding of reaction rate concepts. It was also found that some of the misconceptions were still held by the students in both groups. In the control group, the proportion of these misconceptions was higher than that of in the experimental group. Moreover, previous learning in chemistry contributed to students' understanding of reaction rate concepts significantly. (Contains 3 figures and 2 tables.)