Although the incidence of carotid atheromatous disease is presumably equal between the right and left carotid arteries, right and left carotid endarterectomies (CEs) may not be performed with equal frequency on the two sides. This study sought to examine whether right and left CEs are performed with equal frequency and whether there are any differences in outcome between these groups. Detailed chart review was performed on all CEs performed from 1979 through 1998 at our institution, and those lacking side data were excluded. Data were collected on the side of the procedure, demographics, comorbid conditions, details of the procedure, hospital stay, and major complications. The surgeons performing CE were surveyed about their practice of considering side factors. CE was performed on the left in 1190 (52%) of 2305 procedures; 1115 (48%) of the procedures were right CEs. This difference is statistically significant (P = 0.014). No significant differences in demographics, comorbidity, presence of symptoms before surgery, length of stay, or postoperative morbidity or mortality between the left and right groups were found. A majority of the surgeons surveyed indicated they do consider the relationship of side of the carotid disease to the patient's dominant side. The significant difference in the performance of left CE more often than right has not been previously reported. This may reflect willingness by surgeons to intervene more frequently in carotid disease on the side supplying the dominant hemisphere. A prospective CE outcome study that identifies the side of CE and the patient's dominant side is needed for further exploration of this issue.