Over a two-year period, 100 venous angiograms were performed on 75 patients because of difficulty with vascular access. Seventy percent of the patients had decreased arterial flow or increased venous resistance. High output failure, sepsis, and aneurysm formation were also found. Venous angiography of the fistula demonstrated significant stenosis in 40% of the cases as well as total occlusion by thrombus in 9%, aneurysm formation in 7%, and abnormal fistula needle placement or anatomic abnormalities in 20% of the cases. Definitive diagnosis with the aid of venous angiography permitted specific surgical intervention in 62% of the cases, and identified new sites for needle placement in 18% of the cases, thus prolonging fistula life and reducing the need for new fistula placement. Our experience with local cellulitis of the fistula site and sepsis is also discussed.