['Octogenarians and even patients over 70 years old have unexplained poor outcomes with carotid angioplasty and stenting (CAS). We sought to evaluate whether older patients may have compromised intracranial collaterals and cerebral reserve and be intolerant to otherwise clinically silent emboli generated during CAS.', 'One thousand twenty-four cerebral blood flow (CBF) studies performed between 1991 and 2001 with stable xenon computed tomography scans (Xe/CT) were reviewed. CBF was measured before and after 1 gm intravenous acetazolamide (ACZ), a cerebral vasodilator. The normal response to ACZ is an increase in CBF. In areas of significant compromise of cerebral reserve (CR), CBF drops, representing a "steal" phenomenon. CBF changes were categorized as normal or abnormal and correlated with age, gender, cerebral symptoms, and with intracranial, carotid, or vertebral artery disease. Logistic regression was used to determine the effect of age on CR in the entire group and a subgroup of 179 patients with significant carotid stenosis of >50%.', 'Nine hundred sixteen studies were suitable for analysis. Carotid occlusion was predictive of decreased reserve (OR, 3.9; P = .03) regardless of age. There was also a trend toward lower reserve with severe carotid stenosis >70% (OR, 3) and in women (OR, 1.8; P = .08). Age >or=70 had no effect on reserve in the overall heterogeneous population with and without carotid disease and neither did a history of stroke, carotid, or intracranial stenosis. However, in 179 patients with significant carotid stenosis, age >or=70 was predictive of poor reserve (OR, 2.7; P = .03) and so was the presence of peripheral vascular disease (OR, 3.7; P = .03). A trend toward decreased reserve was also seen in women (OR, 2.3; P = .08).'] Is cerebral reserve decreased in elderly patients with carotid stenosis?