Purpose: To assess the effectiveness of educational HIV/AIDS prevention programs in two medical universities in Shenyang, China. Methods: Changes in HIV/AIDS knowledge and attitudes were evaluated following an educational intervention program involving 2,418 graduate medical students (n=1,319 intervention group, n=1,099 control group), which was delivered by a final team of 32 medical student peers who had been trained to be trainers for the current study. Results: Following the training, 72.6% of the students learned that mosquito bites cannot transmit HIV. Students also learned that sharing a toothbrush (66.9%) and hairdressing implements (63.3%) can transmit HIV. The learning scores were somewhat lower for the items “Exercise cannot reduce the risk of HIV transmission (49.7%)” and “HIV transmission from male to female is greater than female to male (44.7%).” While there were significant improvements in knowledge and/or attitude scores between the pre- and post-test in the intervention group, no significant changes were found in the control group. Conclusion: The overall finding indicates that peer education improves HIV/AIDS-related knowledge and attitudes among medical students from the two universities. Limitations: The results of this study cannot be generalized to other population groups since medical students are more knowledgeable on health topics than the general population. The study was limited to two medical universities. A broader segment of the medical universities should be chosen for future studies. Peer education should also be related to student scholastic accomplishments to determine if results are modulated by factors such as student motivation or academic acumen as roughly reflected in grades. These results could have also been influenced by other external information sources.