We evaluated the effect of troglitazone (given orally 400 mg/day) on glucose intolerance and on the plasma levels of tumour necrosis factor-alpha (TNF-alpha) in 12 obese patients with type 2 diabetes for 12 weeks. Troglitazone significantly decreased fasting plasma glucose, serum C-peptide, serum insulin and HbA1c levels. Plasma levels of TNF-alpha were significantly reduced by troglitazone administered for 8 and 12 weeks. Troglitazone administration significantly improved insulin resistance, but did not affect pancreatic beta-cell function as evaluated by the homeostasis model assessment (HOMA). In the present study, we reported for the first time that troglitazone administration significantly reduces plasma levels of TNF-alpha in obese patients with type 2 diabetes.