The study was conducted to determine the clinical pattern and etiology of cerebral venous thrombosis in Iran. Records of all adult patients admitted with a clinical diagnosis and MRI of cerebral venous thrombosis from 1993 through 1999 in three major hospitals of Tehran, Iran were reviewed. Fifty patients (39 women, 11 men) aged 14 to 56 years were identified. Headache the most frequent and often the earliest symptom, was encountered in 82 percent and papilledema, the most frequent sign in 56 percent of cases. Infection was the cause of cerebral venous thrombosis in 26 percent of our cases. Other causes included oral contraceptive (32 percent), vasculitis (6 percent), Behcet's disease (4 percent), postpartum state (4 percent), myeloproliferative disease (2 percent), ulcerative colitis (2 percent), antithrombin III deficiency (2 percent) and diabetic ketoacidosis (2 percent). Oral contraceptive was recognized as the most common etiology. Infection is an important cause whereas procoagulation disorders are uncommon.