Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA) and stenting is well described, as well as different mural pathology in primary versus post-carotid endarterectomy (CEA) restenosis lesions. The purpose of this study is to investigate possible different patterns of embolization in regards to number and distribution of microembolic signals (high-intensity transient signals (HITS)) in patients with primary carotid stenosis and restenosis after CEA. We used transcranial Doppler (TCD) to monitor the ipsilateral middle cerebral artery (MCA) of 13 patients (13 procedures) with restenosis after CEA and six patients (seven procedures) with primary stenosis of the internal carotid artery (ICA) during PTCA and stenting. All the procedures were performed without protection devices. The total number of HITS recorded in all patients was 2692, including 1563 microemboli in patients with restenosis and 1129 in patients with primary stenosis. The mean number of microemboli per procedure was 120.2 ± 65 and 161.3 ± 70 (p = 0.05) respectively. The average number of microembolic signals during the various stages of PTCA and stenting in the two groups was as follows: 1. Crossing the stenotic region with the guidewire and positioning the balloon inside the stenosis 33 ± 6.9 and 73.4 ± 9.4 (restenosis patients versus primary-stenosis patients, respectively,