In Reply.—We appreciate the comments by Lynfield concerning our article "Non-Invasive Evaluation of the Extracranial Carotid Arteries in Patients With Cerebrovascular Events and Atrial Fibrillation." We are gratified that he concurs with our theme that patients with atrial fibrillation may have other sources of cerebral ischemia in addition to thromboembolism from the atrium. Our data cannot answer all of the questions Lynfield raises, because the study was performed retrospectively and did not address all these issues. We are currently participating in the "Stroke Prevention in Atrial Fibrillation" trial, which is designed to clarify these points in a prospective manner. Hopefully, the results will be available soon so that we can further understand the mechanisms of cerebral ischemic events in patients with atrial fibrillation.