The purpose of this study was to investigate the effectiveness of an ongoing AIDS education intervention program (EMIMA) using peers in a sport context. A secondary purpose was to determine whether a mastery-based motivational strategy would enhance the effectiveness of the peer coaches. A quasi field experimental study was employed in which at-risk children in Dar es Salaam in Tanzania (N=764) were recruited (average age=13.6 years) and were randomly grouped into two treatment groups and two control groups. The treatment groups were peer coaches conducting the AIDS education to the children within sport, one with mastery coaching strategies and one without. The two control groups were in-school children, who received traditional AIDS education, and out-of-school children, who received no education at all. The intervention lasted for 8 weeks. The results indicated that the intervention using peers in sport was more effective in transmitting HIV prevention knowledge, cognitions and perceived behaviors than the control groups. The mastery-based motivational strategies were effective in influencing some of the variables. Contrary to expectation, the school-based HIV education was no more effective than the informal education obtained by the out-of-school children. The use of peer coaches within the EMIMA program was reliably the most effective means for HIV/AIDS education for these at-risk children.