Chronic renal failure (CRF) results from chronic reduction in renal functions, in which the main feature is a decrease in glomerular filtration rate (GFR). Endothelial cells produce endothelin (ET) which is the most potent vasoconstrictor polypeptide. ET was found in the kidneys. It’s renaleffects include increase in renal vascular resistance and decrease in GFR. This study was done to assess the difference between the effect of hemodialysis and peritoneal dialysis on ET level changes in patients with CRF. The results showed that peritoneal dialysis provides better clearance of ET.