Objective: To examine the effect of diabetes mellitus on sex hormones. Methods: This was a prospective study. Patient selection was done by simple random enrollment of adult males and females after confirmation of their diagnosis on the basis of WHO criteria i.e. fasting venous plasma glucose concentration of more than 140 mg/ dl (7.8 mmol/l) and /or more than 200 mg/dl (11.1 mmol/l) two hours after carbohydrate meal or two hours after the oral ingestion of the equivalent of 75 g of glucose. Serum testosterone was determined by a double antibody radioimmunoassay (RIA), using a Gamma-B Testosterone kit and serum oestradiol was determined by a double antibody radioimmunoassay (RIA) using a Gamma - B - direct oestradiol kit. Results: The levels of testosterone were significantly (P<0.01) decreased in both insulin dependent diabetes patients as well as in non-insulin dependent diabetes patients. However, the results of the non-insulin dependent diabetes patients particularly in male on different treatments showed slight but significant decline in testosterone levels. In uncontrolled diabetes patients negative impact upon sexual function was associated with defective reproductive capacity. Conclusion: The development of decreased reproductive capacity and impotency in uncontrolled diabetes highlights the need for taking measures to control the development of diabetes mellitus at earlier stage.