Eighty-five patients were followed up at least 1 year after creation of an arteriovenous fistula in the forearm. The anastomosis was side-to-side in 33 patients, end-to-side in 33 and end-to-end in 19. Trophic lesions were not observed. Intermittent claudication of the hand was more frequent in patients with a side-to-side arteriovenous fistula (42 percent) than in those with end-to-side (21 percent) or end-to-end fistulas (16 percent). Clinical and x-ray studies indicate that two different mechanisms are responsible for cramping pains: arterial steal phenomenon and venous hypertension. Their relative importance depends on multiple hemodynamic factors that may vary with time.