Congenital arteriovenous malformations confined to the soft tissues of the pelvis are rare and challenging lesions. Multitudinous embryonic macrocommunication and microcommunication between the arterial and venous systems, with resultant shunting of blood to the low-resistance veins, produce massive venous and tissue engorgement. No well-established guidelines exist concerning their management. Percutaneous arterial embolization and surgery are associated with high recurrence rates. Surgical excision is frequently not possible and can result in massive hemorrhage. Only 52 cases have been reported in the English-language literature, and only two patients were followed for longer than 6 years. This report presents two additional patients with massive pelvic arteriovenous malformations monitored for 9 and 17 years. One patient was initially treated with arterial percutaneous embolization and the other with attempted operative ablation. A review of the literature has allowed us to develop the following management guidelines: Asymptomatic, nonenlarging lesions require no intervention and can be safely followed by clinical and radiologic (ultrasonography, CT scanning) examinations every 6 months. Symptomatic or rapidly enlarging lesions should be treated with preoperative arterial embolization and surgical excision attempted only if the arteriovenous malformation is localized and does not involve adjacent organs. Arterial embolizations may be repeated to provide symptomatic relief of diffuse, large lesions that involve the bladder or bowel. This protocol will avoid unnecessary and frequently life-threatening surgery in the management of pelvic arteriovenous malformations.