Introduction: Randomised trials have shown that successful carotid endarterectomy (CEA) approximately halves 5-year stroke risk among patients with tight asymptomatic carotid artery stenosis. The benefits of CEA with current medical therapies (including higher dose statins) are unclear. A reliable estimation of stroke risks requires follow up of a large cohort of patients with unoperated asymptomatic carotid stenosis and this report describes the design and characteristics of patients being recruited to this UK Carotid Cohort Study. Methods: Patients are recruited prospectively from three UK NHS hospitals when they present to vascular laboratories for carotid duplex assessment. They are invited to join, asked to complete a one page consent form and medical questionnaire and their carotid duplex assessments are then performed by accredited vascular scientists. Enrolled patients will be followed for up to 10 years by electronic data linkage and identified strokes characterised by review of hospital medical records and cross-sectional cerebral imaging. Results: Over seven hundred patients presenting for carotid duplex imaging have now been enrolled (∼40 per month). Approximately two-thirds are men, their mean age is 70 years. 12% report a prior stroke, 15% report ischaemic heart disease and 17% have diabetes. At the time of imaging, just over half (53%) were taking an antiplatelet agent, 71% took antihypertensive medications and 64% were on cholesterol-lowering medication. Nineteen percent had flow-limiting carotid stenosis (exceeding 50%). By the end of 2019, 1000 patients will have been recruited and 5-year stroke rates for this cohort will be reported in 2024. Conclusion: This vanguard study shows that large numbers of patients can be recruited from vascular laboratories. A full-scale study of 10,000 patients is now being planned, which will provide contemporary and representative estimates of stroke risk among patients with unoperated carotid stenoses. This data, in conjunction with existing and future trials, will help clarify the potential benefits of carotid revascularization in asymptomatic patients. Disclosure: Nothing to disclose