There is a wide variety of disorders associated with thrombosis of the superior sagittal sinus (SSS), including infectious disease. noninfectious conditions such as vasculitis and hypercoagulable states, and complications arising from pregnancy or use of oral contraceptive medications. Despite these well-defined associations, approximately 25% of the cases remain idiopathic. In this article the authors describe a patient who was found to have SSS thrombosis while experiencing a thyrotoxic phase of Graves disease. The patient presented with intracerebral hemorrhage, subarachnoid hemorrhage, seizure, coma, a raised fibrinogen concentration, low protein C activity, and atrial fibrillations. Thrombolysis was successfully performed despite the coexistence of thrombosis and intracranial hemorrhage. Patients with thyrotoxicosis and a diffuse goiter may be predisposed to the development of SSS thrombosis, as a result of hypercoagulation and stasis of local venous blood flow. In the present case, a patient in whom thrombosis coexisted with intracranial hemorrhage was successfully treated using thrombolytic therapy.