Several observation studies have reported an association of insulinresistance with low serum testosterone level in men. A link betweentestosterone deficiency and diabetes has also been suggested with thedemonstration that men with type 2 diabetes have lower testosterone levelthan weight matched non diabetic control subjects. In addition lowtestosterone may predict development of type 2 diabetes and features of themetabolic syndrome. We hypothesized that testosterone is an important modulator ofinsulin sensitivity. Thus, the aim of this study was to examine therelationship between serum testosterone level and insulin sensitivity in menacross a wide spectrum of insulin sensitivity and dissect the role of obesityin mediating this relationship. This study included 60 subjects : 20 patients with type 2 diabetes mellitusand 20 subjects with metabolic syndrome and 20 subjects as a control groupfor every subject the following were done :-- Full clinical examination- Anthropometric measurement height, weight, waist circumference andhip circumference.- Biochemical analysis for total cholesterol, triglycerides ,fastingblood sugar , fasting insulin and total testosterone.Regarding correlation between total testosterone level and insulin sensitivitywhich is the main concern of study, a statistically highly significantcorrelation between testosterone level and fasting insulin and HOMA and –IR score was found reflecting important association between lowtestosterone and insulin resistance.