Background and objectives: Radiation treatment in nasopharyngeal carcinoma (NPC) is known to be associated with increased prevalence of carotid stenosis. The objectives of the study was to determine the prevalence of radiation-induced extracranial carotid stenosis, plaque, carotid intima thickness (CIMT) in NPC patients; to explore whether the stenosis is due to direct effect of radiation rather than general tendency to atherosclerosis. Methods: This was a cross-sectional study conducted in the University Malaya Medical Centre from July 2011 to February 2012. The study subjects consisted of 47 NPC patients who were treated with radiation, and 47 healthy control. The patients and control had carotid duplex ultrasound and transcranial Doppler (TCD). Results: The mean age of the patients was 55.1 years, the time lapse from radiation was 76.7 ± 95.3 months. Internal carotid artery (ICA) and common carotid artery (CCA) stenosis of ≥50% was seen in 17.0% of patients vs 2.1 % of controls (p = 0.031), with 61.7% of patients and 19.1% of controls having plaque in ICA and CCA (p=0.004). CIMT was increased in 70.2% of patients and 44.7% of controls (p =0.022). Both the patient group and control had similar rate of intracranial stenosis of 12.8% in TCD. Conclusion: Extracranial internal carotid artery is the most common site of stenosis following radiotherapy in NPC. This suggests that local trauma from irradiation is the most important factor in predisposition to atherosclerosis following radiation therapy.