Chylous fistulas are an infrequent result of injury to the thoracic duct during radical neck dissection. Leakage of lymph from a fistula which is allowed to persist will cause such serious postoperative problems as metabolic deficiencies, flap elevation, suture breakdown with hemorrhage, and infection. There appears to be no valid justification for extended conservative management if it fails to slow the leak within 48 hours. We recommend prompt exploration of the wound with an operating microscope and microsurgical ligation of the lacerated duct with nonabsorbable sutures.