Thrombosis of intracranial sinuses and veins is a rare but potentially lethal syndrome. It often affects young adults, but occurs in all ages. It is frequently seen in association with hormonal changes (puerperium, pregnancy and the use of oral contraceptives), inflammatory bowel disease, cancer, and various states of hypercoagulability, or as a consequence of infection. The clinical picture is extremely variable and the diagnosis can be difficult unless one specifically searches for it. The combination of magnetic resonance imaging and magnetic resonance angiography is a powerful and non-invasive tool for diagnosing the syndrome. Treatment with heparin (and for the septic form antibiotics) improves the outcome.