BACKGROUND Insulin resistance (IR) is common among patients on dialysis and is worse among patients on peritoneal dialysis (PD) than among patients on hemodialysis. In this study we tested the hypothesis that administration of telmisartan, an angiotensin II type 1 receptor antagonist, might improve insulin sensitivity in patients on PD. METHODS This was a crossover study of 30 nondiabetic patients with end-stage renal disease being treated with PD. Group A patients (n = 15) received telmisartan and other antihypertensive drugs for 4 months, followed by 4 months without telmisartan. Group B patients (n = 15) received their usual treatment for 4 months, followed by 4 months of treatment with telmisartan. Blood glucose and serum insulin levels were monitored and homeostasis model assessment method for IR (HOMA-IR) was calculated. RESULTS Treatment with telmisartan had no significant impact on serum glucose, potassium, and bicarbonate levels. However, telmisartan significantly reduced serum insulin levels and the HOMA index in groups A and B. CONCLUSIONS This study demonstrated that telmisartan, an angiotensin receptor type 1 antagonist, may effectively improve insulin sensitivity as measured by HOMA in patients treated with PD.