Eleven patients with angiographically and/or pathologically verified cerebral sinovenous occlusions not directly caused by trauma were studied by computed cranial tomography (CCT). Static radionuclide brain scans and dynamic radionuclide flow studies were also obtained in four patients; in two, findings diagnostic of lateral sinus thrombosis were noted. These comprised a "negative on dynamic, hot on static" image, as well as a "hot on static with nonfilling on angiography." Computed cranial tomography findings included visualization of the thrombosed vein ("cord sign") or sinus ("empty triangle" or "delta sign"), multiple focal bilateral parasagittal hemorrhages, intense tentorial enhancement, gyral enhancement indistinguishable from infarct, solitary intracerebral hematoma, small ventricles, and normal scan. Excluding the patients with underlying meningioma, all three of whom survived, seven of the remaining eight patients expired during the acute phase of their illness, an 88% mortality. This group includes one patient who had normal CCT findings, albeit without contrast enhancement, who was diagnosed as pseudotumor cerebri. The need for full neuroradiological evaluation, including angiography, is thus stressed if this highly fatal yet treatable condition is not to remain undiagnosed.