Indwelling teflon catheters were introduced percutaneously into femoral artery and vein and then advanced into the aorta and inferior vena cava for the performance of 148 haemodialyses in 30 cases of severe acute renal failure. The patency of the catheters between dialysis was maintained by a teflon external shunt. The blood flow rates varied according to blood pressure. A poor blood flow necessitating the use of a roller pump was constantly observed when systolic B.P. was below 100 mmHg. Clinical side effects have been found in only 2 cases of acute renal failure and severe arterial hypertension. In general this technique has been shown to be safe and of rapid application, usefully indicated in acute renal failure necessitating repeated haemodialysis.