Aim: Testosterone levels correlate not only with insulin sensitivity but also with genetic (OXPHOS gene expression) and functional markers of mitochondrial function (VO2max). A decrease of lean body mass and increase in fat mass are observed in hypogonadal men compared with ageand BMI-matched controls. we are to investigate factors associated with low testosterone levels in type 2 diabetic patients, and the effect of testosterone level on body composition and VO2max (exercise capacity). Method: 30 type 2 diabetic patients who’s bood sampling including Total and free testosteronewas donebetween6AMand9 AM.Measuredmetabolic parameterswereHgbA1C, 24hUrine Protein and C-peptide, fasing glucose and insulin for HOMA-IR calculation, lipid profile.Whole body compositionwasmeasuredbyDEXA. VO2max was obtained using an incremental work conducted with a bicycle ergometer combined by continuous analysis of expired gas and minute ventilation. Results: Hypogonadal men had a significantly lower VO2max (ml/kg/min) than eugonadal Men (27.1 vs 30.9: P<0.05). Age had a significant negative relation with testosterone and free testosterone levels. Total fat mass, central fat mass, lean body mass was not signicantly associated with testosterone levels. Total and free testosterone levels did not have any positive effect on insulin resistance index and lipid profile. Rather than total testosterone levels, free testosterone level has amore powerful biologic effect on exercise capacity (VO2max). Conclusion: Age is a sole significant predictor of total and free testosterone levels. Both Total and Free testosterone is not significantly associated with body coposition in type 2 DM. Free testosterone has a more significant biological effect on VO2max. Because significant number of patients had a long disease duration and most patients had been taking medication and/or subcutaneous insulin, HOMA-IR was not significantly associated with VO2max and Testosterone levels.