Differentiation is often difficult between vascular graft occlusion and progression of underlying disease in patients after vascular surgery. We have studied 57 patients after surgery for traumatic and atherosclerotic arterial occlusion and other vascular anomalies using a commercial digital subtraction angiography (DSA) unit; no complications occurred. Indications for examination included pain, diminished pulse, and failure of catheter angiography. Graft patency was established if proximal and distal anastomoses were visualized; occlusion was diagnosed if no graft was imaged or vascular stump found--noted in 31 grafts. Our diagnosis was proved surgically in 24 patients (two refused operation); three others were confirmed angiographically and one by Doppler ultrasonic examination. In our experience DSA is a safe, specific means of following postoperative grafts and diagnosing their occlusion.