This study examined the incidence and mechanism of restenosis after carotid endarterectomy (CEA) in Japanese patients. To determine the optimal management for carotid restenosis, we retrospectively compared re-CEA with stent placement. One hundred and twenty-six patients who had received 135 CEA with primary suture were studied with angiography or duplex ultra-sonography as a follow-up study to detect restenosis (> 50% diameter reduction). Data was collected regarding demographics of the patients suffering restenosis, including age, sex, other risk factors. Recurrent carotid stenosis (more than 50% stenosis) developed in 9 CEA sites (6.7%) during a mean follow-up interval of 11.0 months (4.7-46.7 months). Recurrent carotid stenosis occurred to a significantly higher degree in women (p = 0.015). There was no significant difference in other risk factors. All patients who developed carotid restenosis were asymptomatic. Re-do CEA and carotid stenting were used to treat restenosis in 3 and 5 patients, respectively. No operative procedure was performed in the remaining one patient with milder restenosis (55%). The 30-day stroke morbidity-mortality rate was 33.3% in CEA and 0% in stent placement. In only one of 4 early restenosis patients, there was a bright lesion in diffusion weighted MR images after stent placement. To treat restenosis after CEA, stent placement is indicated because of a lower risk of distal emboli and there being no need to dissect the previous wound. To prevent restenosis, through plaque removal is necessary and patch closure may be needed especially in females.