Undergraduates enrolled in a Personalized System of Instruction (PSI) (Keller Plan) section of Principles of Educational Psychology at Mississippi State University were subjects in a study of the effects of no review (NR), review questions (RQ), and review concepts (RC), on short-term retention in a PSI class. The NR group received no review. The RQ group received review questions from the previous unit on their unit mastery tests. The RC group received review concepts from the previous unit. The test of retention was a multiple choice exam constructed by the investigators. A completely randomized blocking design was employed to analyze the data. The blocking variable was grade point average. The data were analyzed for the complete test of retention and for a subset of review-related questions. No significant differences were found among the NR group, the RQ group, and the RC group on a test of retention, a finding supported by previous research. No signficant differences were found between the higher grade point average group and the low grade point average group. References and an appendix with several sample review questions are provided. (Author/LC)