The purpose of this study was to assess the effect of rosiglitazone on bioavailable, free and total testosterone levels in hypogonadal men with type 2 diabetes. Sixteen type 2 diabetic men with hypogonadism were studied before and after administration of rosiglitazone (8 mg/day) for six months, with assessments performed every two months on two consecutive days. We measured testosterone and sex hormone binding globulin (SHBG), visceral adiposity, high-sensitivity CRP (hs-CRP), lipids, microalbuminuria and blood pressure. There was a significant increase in free (p=0.01), bioavailable (p=0.007) and total testosterone (p=0.002), as well as SHBG (p=0.03) levels, with rosiglitazone treatment. Waist circumference and waist / hip ratio decreased with the improvement in insulin sensitivity and glycaemic control (p=0.01). There was also a significant reduction in hs-CRP (p=0.02) and urinary albumin excretion. No significant effect on blood pressure or the ratio of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol (LDL to HDL) was seen. In conclusion, the insulin-sensitiser rosiglitazone increases bioavailable, free and total testosterone and SHBG levels in hypogonadal men with type 2 diabetes.