Background and Purpose— Carotid angioplasty and stenting (CAS) has a higher incidence of periprocedural stroke compared with endarterectomy. Identifying CAS steps with the highest likelihood of embolization may have important implications. We evaluated CAS safety by correlating the findings of procedural transcranial Doppler with postprocedure diffusion-weighted imaging (DWI) lesions. Methods— In this prospective study, transcranial Doppler monitoring was performed during CAS procedures, which were divided into 11 steps. Embolic signals on transcranial Doppler were counted and classified based on the relative energy index of microembolic signals into microemboli ≤1 or malignant macroemboli >1. Poststenting MRI was performed in all cases. A negative binomial regression model was used to evaluate the predictive value of transcranial Doppler emboli for new DWI lesions. Results— Thirty subjects were enrolled. Seven of 30 subjects (23.3%) were asymptomatic. The median embolic signal count was 212.5 (108 microemboli and 80 malignant macroemboli). Stent deployment phase showed the highest median embolic signals count at 58, followed by protection device deployment at 30 ( P =0.0006). Twenty-four of 30 (80%) had new DWI lesions on post-CAS MRI. The median DWI count was 4 (interquartile range 7). Two of 30 (6.7%) had new or worsening clinical deficits post-CAS. For every malignant embolus, the expected count of DWI lesions increases by 1% ( 95% confidence interval, 0%–2%; P =0.032). Conclusions— We observed a high incidence of embolic signals during CAS procedure, especially, when devices were deployed. Most subjects developed new DWI lesions, but only 6.7% had deficits. Malignant macroemboli predicted new DWI lesions.