BACKGROUND Thrombus within the carotid artery usually occurs in vessels with severe atherosclerotic disease and may embolize to cause transient ischemic attacks and cerebral infarctions. The risk factors for carotid artery thrombus formation in the absence of atherosclerosis are not well characterized. A case series is presented that suggests an association of carotid artery thrombus with severe iron-deficiency anemia and thrombocytosis. METHODS We describe three women with severe iron-deficiency anemia and thrombocytosis secondary to menorrhagia who developed carotid artery thrombi. Thrombi were detected radiographically. The patients were treated with anticoagulation and antiplatelet therapy. In two patients, follow-up neuroimaging 10 to 14 days later demonstrated resolution of the thrombus and no identifiable vascular disease. CONCLUSIONS Severe iron-deficiency anemia with thrombocytosis may be a risk factor for carotid artery thrombus formation. Medical management with anticoagulation and antiplatelet therapy is a reasonable approach for these patients while the thrombus resolves.