These 2 case histories of rapidly fatal intracranial venous thrombosis in Swiss women taking oral contraceptives include detailed clinical history necropsy and histology. The first was 50 years old and had taken Noracyclin (5 mg lynestrenol and .15 mg mestranol combined) for 14 days of vaginal bleeding and testosterone for 7 months preceding. She suddenly became unconscious had seizures neck stiffness blood in cerebrospinal fluid congested retinal veins slight fever and died the following day. The brain had a clot throughout the superior sagittal sinus and thrombosis of several anastomotic veins; histologically these clots were unorganized and not recanalized. The second woman 41 years had taken Ovulen (1 mg ethinodiol diacetate and .1 mg mestranol combined) for 6 months for menstrual disturbance. She noticed numbness in her right hand entered hospital and collapsed a few hours later. A left carotid angiogram showed an intracerebral left parietal hematoma which was removed. She died 2 days later. Pathologic diagnosis was thrombosis of superior sagittal sinus anastomotic veins and veins of pia mater of the left cerebral cortex. The clots had a high fibrin content and were not recanalized. Histologic sections of both cases demonstrated endothelial thickening of the lateral lacunae of the dura mater suggestive or recanalized recurrent thrombosis occurring a few days before the final episode. Degeneration of elastica and thickening of the intima in arterioles were seen in both cases.