Cerebral venography and manometry in nine patients with idiopathic intracranial hypertension consistently showed venous hypertension in the superior sagittal sinus and proximal transverse sinuses, with a significant drop in venous pressure at the level of the lateral third of the transverse sinus. The abnormality, clearly demonstrated by manometry, was not well shown on the venous phase of cerebral angiography. The appearance of the transverse sinus on venography varied from smooth tapered narrowing to discrete intraluminal filling defects that resembled mural thrombi. Two patients with intracranial hypertension due to minocycline did not show venous hypertension.