Results of a study that investigated the effects of instructor-pacing and self-pacing in a personalized system of instruction (PSI) course on student withdrawal rate, achievement, and attitudes are discussed in this speech. Sixty-two Arizona State University students enrolled in a political science introductory research course were randomly assigned to either a self-paced or an instructor-paced group. Results show that 10 of the 30 students (33 percent) in the instructor-paced group and 21 of the 32 students (66 percent) in the self-paced group withdrew from the course. No significant differences were found between groups in attitudes or achievements. It is therefore considered that the use of instructor-pacing in PSI courses can reduce the number of withdrawals without having adverse effects on student achievement or attitude. Other procedures that might reduce withdrawal rates in PSE courses, which are reported as higher than lecture-discussion courses, are suggested. (SPG)