An 80-year-old woman was discovered to have a left femoral AV fistula on catheterization for right iliac endovascular angioplasty. The patient had had cardiac catheterization via the left femoral artery several years before. No intervention was undertaken at the time of discovery, but the patient subsequently developed high output congestive heart failure and repair of the fistula was mandated. Filling of the left femoral and external iliac vein from the femoral artery is demonstrated on these sequential angiogram images.