Introduction The purpose of our study was to evaluate the ultrasonographic characteristics of recurrent carotid stenosis in patients submitted to carotid endarterectomy with patch angioplasty. Methods We performed carotid ultrasound examinations on patients who had undergone unilateral carotid endarterectomy between 2002 and 2009. Patients with bilateral and/or endovascular procedures were excluded. All ultrasound examinations were performed by the same registered vascular technologist. Results One hundred male and 25 female patients were studied. The average time between surgery and the ultrasound examination was 38.8 months (range, 3–99.2 months). Twenty-nine (23.2%) patients had recurrent carotid artery stenosis after unilateral endarterectomy. Of these, 17 patients were found to have recurrent carotid artery stenosis classified as <50%; 7 patients had recurrent stenosis in the range of 50% and 69%, and 5 patients had >70% diameter-reducing lesions. Plaques associated with recurrent carotid stenosis were significantly less echogenic, more acoustically homogenous, and had a smoother surface contour. Compared with the primary carotid stenosis (nonintervened side), plaques associated with recurrent carotid stenosis were more often hypoechoic (58.6% versus 8.1%), acoustically homogenous (69% versus 44.6%) and smooth-surfaced (93.1% versus 74.3%). Also, the longer the interval between surgery and the carotid sonographic examination, the more similar the ultrasonographic characteristics were between the two groups. Conclusions The different sonographic characteristics of primary carotid stenosis and recurrent stenosis after carotid endarterectomy in the same patients, are associated with different outcomes for the two conditions. There is a current clinical consensus that patients presenting with recurrent symptoms after carotid endarterectomy should be treated, but the best management for asymptomatic patients with recurrent carotid artery stenosis remains uncertain.