Although many older adults start to participate in regular exercising, lack of guidance often results in program inefficiency and discontinuation. The peer mentor model has been used successfully elsewhere and has been theorized to be effective in fitness settings. The purpose of this study was to document the retention rates and changes in physical fitness for older adult subjects trained by peer-mentors in comparison to subjects trained by qualified Kinesiology student trainers. Stage 1 of this study identified 30 older adults with a mean (± SD) age of 68.6 ± 5.8 years to participate in a 30-week physical training and mentorship skill development program. After the 30-week preparation program, 60 new participants were recruited for Stage 2 and divided into two groups: 1) Student Mentored (SM) group (N=30); and 2) Peer Mentored (PM) group (N = 30). Mean (± SD) age of the recruited subjects was 68.7 ± 6.1 years. The 35-week intervention program for the new subjects included three 75-minute training sessions per week. The exercise programs for the SM and PM groups were identical. SM and PM group subjects completed a battery of fitness tests at the start and conclusion of the intervention to include: the 30-second chair stand and arm curl strength tests; the 6-min walk endurance test; the forward reach balance test; and the 8-ft up-and-go agility test. Fitness performance data were analyzed using one-way analysis of variance (ANOVA). With the exception of the 30-second chair stand test, there were no significant differences between the SM and PM groups at baseline. Nineteen SM and nineteen PM group subjects completed the 35-week training program, thus retention was equally 63% in both groups. Compared to baseline values, improvements in fitness measures ranged from 11.2% to 58.0% and all improvements were statistically significant for the SM and PM groups (p<0.001). At 35 weeks, fitness test means for the SM group were slightly higher than for the PM group, but the differences were not statistically significant (p>0.08) for any measures. Through the well-designed physical training of this intervention the ability of older adults to improve their physical fitness was demonstrated. The equal retention rates between the experimental groups and the lack of significant differences in the fitness measures at the conclusion of the intervention indicated that peer-mentors were similarly effective in training older adults as qualified Kinesiology student-trainers.Keyword(s): aging/older adult issues, community-based programs, exercise/fitness/physical activity