This study examined the impact of two approaches to use of student response systems (SRSs) on achievement in a study designed to better understand effective use of the devices. One condition was anonymous use of SRSs, in which graduate students selected a random clicker when entering the classroom. The second condition assigned devices to students for use throughout the semester. Two treatment and two control classes were tested, with dependent variables including percent of correct responses to questions posed in classes, performance on the midterm exam, and performance on the final exam. Results indicated that students who were assigned to specific units during the term had a higher percent of responses correct than the control group students on in-class questions. However, performance on the midterm exam and final exam was not significantly different among students in the two SRS conditions, suggesting that the benefits of SRS use can be derived from anonymous use. (Contains 4 tables.)