While the development of a spontaneous iliac arteriovenous fistula is an uncommon complication of arteriosclerotic aneurysmal disease, its association with a distinct clinical syndrome allows timely operative intervention for this potentially life-threatening event. A review of cases reported in the literature reveals a triad of symptoms consistently associated with the presence of a spontaneous iliac arteriovenous fistula: high-output cardiac failure of precipitous onset, a pulsatile abdominal mass accompanied by a thrill and bruit, and unilateral lower-extremity ischemia or venous engorgement. Survival may be anticipated if an aggressive diagnostic and operative approach is employed.