Adequate venous outflow is critical to the proper function of a vascular-access graft (arteriovenous fistula) used for chronic hemodialysis. Stenosis of the subclavian vein can significantly compromise this venous outflow. The development of such subclavian vein stenoses has been associated with the prior placement of temporary subclavian vein dialysis catheters. We evaluated the importance of preoperative detection of these stenoses before placement of a permanent vascular-access graft in the upper extremity. Upper extremity venography was performed before placement of a permanent vascular-access graft in 43 patients. A total of 62 extremities were evaluated. A 40% prevalence of moderate or severe subclavian vein stenosis was found in patients with prior or existing temporary dialysis catheters in the subclavian vein. No stenoses were found in patients without a history of dialysis catheters in the subclavian vein. This difference in the prevalence of subclavian vein stenosis is statistically significant (p less than .001). In no case was the stenosis suspected clinically. Before placement of a permanent vascular-access graft, the subclavian vein should be evaluated in all patients with a history of a temporary dialysis catheter in the subclavian vein. The use of sites other than the subclavian vein for temporary dialysis is strongly encouraged.