This study examined the effects of physical fitness training and reinforcement on adults who were institutionalized and dually diagnosed as mentally retarded/emotionally disturbed. Subjects (N=5) were provided daily 1-hour fitness training sessions for 6 weeks. Fitness data were collected before initial fitness training, after 3 weeks of training, after 1 week of no fitness training, after 3 more weeks of training, and 2 weeks after training was terminated. Fitness data collected included total number of bent-knee sit-ups completed in 1 minute, total distance in feet completed in 12 minutes of running, and flexibility in centimeters measured on a sit-and-reach box. An equivalent time-series research design (A-B-A-B) with follow-up was used to test the relationship of fitness training and reinforcement to subsequent fitness component behaviors. The results for both individual and group data show improvement in all three fitness parameters after 3 weeks of training and continued improvement for the final 3 weeks of training. The results of a two-way ANOVA yielded significant differences of training and reinforcement for all three fitness parameters across research phases and follow-up.