OBJECTIVES:   To estimate the threshold of relative stroke risk needed that makes medical management inferior to protected carotid stenting in asymptomatic patients with carotid artery stenosis and substantial cardiovascular comorbidities. METHODS:   A validated and published Monte Carlo microsimulation model created a stroke-free, two-year survival curve in monthly increments for a hypothetical medically managed arm of a recent single-arm carotid revascularization trial in patients at high surgical risk due to their cardiovascular comorbidities. Using a log rank test the actual two-year survival curve from the ACCULINK for Revascularization of Carotids in High-Risk patients (ARCHeR) trial data was compared to the medically-managed curve generated by the model.  The model stroke risk equations were generated from the general population and calibrated for patients with asymptomatic carotid artery stenosis but otherwise healthy. Relative stroke risks between these patients and the surgical high-risk patients were estimated from the stroke rates of the intervention arm of a trial with more restrictive inclusion criteria (ACAS) and the strokes rates of ARCHeR. RESULTS:   Using the best estimate of relative risk (2.02) the one- and two-year stroke rates for medical management were 0.901 and 0.851, respectively. This compares to 0.934 and 0.879 from the ARCHeR trial using protected carotid stenting. The Chi-square statistic from the log rank test of two-year survival curves was 2.26; p=0.13 that medical management produces different results from carotid stenting.  As long as the relative risk is greater than 2.25 the p value is <0.05. CONCLUSIONS:  Recent carotid stenosis trials lack medically managed populations, but a model can estimate stroke-free survival and mortality data for these patients if the relative risk compared to a known population can be estimated.  Since the ARCHeR trial found no ipsilateral strokes in its third year, this two-year analysis may overestimate the relative risk needed to justify carotid stenting.