This study presents the results of an evaluation of a peer-based HIV/AIDS education program, the BASE program, as implemented in a suburban high school setting. The participants were 132 high school students who participated in an "AIDS Awareness Day" as a part of the BASE program in their high school. Each student completed preintervention and postintervention measures of HIV knowledge and attitudes toward HIV/AIDS. Results indicated that no significant change in knowledge was observed from preintervention to postintervention. A significant decrease in fear of becoming HIV infected was observed from preintervention to postintervention; however, other attitudes did not change over time. The results suggest limited effectiveness of the program as implemented in changing student knowledge of and attitudes toward HIV/AIDS. The role of fidelity to the original program is highlighted. This study provides relevant data for individuals and organizations who are responsible for selecting and implementing school-based HIV prevention programs, including health educators and health care providers, administrators, and policymakers.