During a study period from 1977 through 1984, 11 (0.4%) of 2651 patients who had undergone carotid endarterectomy at The Cleveland Clinic had early, symptomatic thrombosis of the internal carotid artery (ICA) and underwent urgent reoperations. With only two exceptions, neurologic deficits occurred after lucid intervals when the patients had recovered from general anesthesia and were discovered within the first 8 hours in three patients, within 8 to 24 hours in five patients, and on the second postoperative day in one patient. Surgical management consisted of thrombectomy alone in two patients, thrombectomy and vein patch angioplasty in eight patients, and thrombectomy of the external carotid artery with ligation of the ICA in a single patient in whom retrograde ICA flow could not be reestablished. Eight (73%) of the 11 patients recovered substantial neurologic function after reoperations, six of whom had complete or nearly complete resolution of their symptoms. One patient (9%) sustained a fatal hemorrhagic cerebral infarction. In a collected series of 41 patients from this study and other reports, prompt surgical treatment of thrombosis occurring after carotid endarterectomy was associated with clinical improvement in 61% of patients and appears to be the preferred approach to this catastrophic complication.