The purpose of this retrospective study was to determine if physiological performance measures were associated with staying in or dropping out of a medically supervised exercise program. In a retrospective file analysis, three subject groups of 35 subjects each were defined by their length of participation in the program. One group, the early drop outs, included subjects who participated in the program for a period of less than six months, another group, the late drop outs, participated for 6-12 months, and the third group, the compliers, was comprised of subjects who complied with the program beyond one year. Measurements were made on the following variables at entry and again after six months of participation: maximal oxygen uptake, resting heart rate, resting blood pressure, serum cholesterol and body weight. U sing analysis of variance for paired groups, the three groups were found not to differ on any performance variable at entry (p > .05). No significant differences were observed between the late drop outs and compliers when identical performance measures were compared at the time of the six month GXT. A paired t-test analysis to determine physiological changes within both the late drop outs and complier groups revealed that neither group had made significant improvements in the physiological indicators over the six month period, except in the oxygen consumption measurement for both the late drop outs and the complier groups, / Master of Science