Arteriovenous fistulas were created on 21 occasions in 18 patients using an interposed segment of processed bovine carotid artery. In 18 fistulas, there were loops in the femoral region, and in three, they were created in the forearm. Seventeen of 21 fistulas developed a useful patency, with useful patency being achieved in 16 of the 18 patients. This patency is impressive, since it provided life-saving vascular access in these patients who previously had had failure of multiple standard shunts or fistulas. However, there was a high incidence of complications, with 17 of 21 fistulas developing some complication. Ten fistulas spontaneously occluded, but flow was restored in six. Seven significant infections occurred in fistulas of the thigh, with one patient eventually dying from complications. In two patients, major hematomas developed, and in six patients, false aneurysms developed, four of these false aneurysms being clearly associated with infection. Venograms were useful in the arm for demonstrating patency of the vein to be used for the arteriovenous fistula. The bovine interposed segment is a useful alternative in patients with difficult vascular access problems for hemodialysis but should be reserved only for such patients.