Cerebral venous thrombosis (CVT) is a distinct cerebrovascular condition that represents 0.5-1% of all strokes in the general population. Because of its procoagulant and antifibrinolytic effects [Horne et al.: J Clin Endocrinol Metab 2004;89:4469-4473], hyperthyroidism has been proposed as a predisposing factor for CVT [Saposnik et al.: Stroke 2011;42:1158-1192]. For the first time, we describe a 22-year-old right-handed woman with a sinus sigmoideus thrombosis due to Graves' disease. Although subclinical hyperthyroidism had been detected 2 years before the onset of neurological symptoms, she did not receive any medical follow-up. Early recognition, diagnosis and treatment are of crucial importance, as Graves' disease is a risk factor for CVT and stroke.