Computed tomography and arterial portography were combined in 12 patients for studies of the anatomy and hemodynamics of the portal venous system. This technique was found to be more sensitive than conventional venous-phase angiograms of the superior mesenteric and splenic arteries for evaluation of the anatomy of the portal venous system and extent of thrombosis in patients with cavernous transformation and also facilitated recognition of subtle evidence of hepatofugal flow and portosystemic shunts. CT portography can be employed when conventional angiograms fail to show the portal vein adequately.