 Studies suggest that testosterone T replacement in healthy elderly men has beneficial effects on body composition, muscle, bone, memory, and behavior, but the risks of chronic treatment, especially on the prostate, heart, and sleep quality, are not entirely clear. Therefore, it is most desirable to supplement into the lowest effective range in elderly men. However, the effects of lower than usual replacement T doses have not been well studied. Furthermore, the possible important interaction of exercise to enhance the positive effects of T supplementation, yet mitigate the possible side effects, has not been studied in older men. 