The authors report their experience with percutaneous nephrostomy in the treatment of acute renal failure due to ureteral obstruction. One hundred and forty-three patients were treated with the positioning of 218 percutaneous nephrostomy catheters under fluoroscopic guidance. If performed as soon as possible, this percutaneous diversion provides a rapid improvement in renal function and allows an accurate staging of the lesion, as well as correct therapeutic indications. In many cases of urinary obstruction interventional radiology procedures represent a valid and successful alternative to more invasive palliative surgery.