The following evaluates a pilot HIV education program conducted in five Texas prison facilities that used male and female prisoners as peer educators. Quantitative data, collected via pre- and post-surveys from 242 prisoners, indicated statistically significant increases in knowledge about HIV/AIDS and nonsignificant improvements in attitudes and beliefs about HIV/AIDS prevention. Qualitative data were collected via interviews with wardens and program coordinators and through focus groups with trained peer educators and their students. These data indicated that program implementation and effectiveness were influenced by a range of common factors including the roles of program coordinators and security staff in program implementation and maintenance, the selection of peer educators and students, curricular content, program promotion and benefits, and logistical considerations (i.e., space, time, and scheduling). Qualitative data also suggested a diffusion of knowledge to other prisoners and facility staff, as well as to family members and friends outside the facility. These data suggest that such a peer-based, risk-reduction education program is both feasible and beneficial in a prison population.