In a comparative study, we showed that a gain in diagnostic reliability justifies the routine use of PGF in indirect superior mesenteric venograms of patients with portal hypertension. Three radiologists without knowledge of patients' data and treatment analyzed 30 angiograms with and 30 examinations without PGF. Complicating factors, such as presence of varices and dose of contrast medium (CM), were taken into account by a Mantel and Haenszel procedure. When PGF was used, intrahepatic portal branches could be outlined beyond their second ramification more frequently. The superior mesenteric and portal veins, but not the confluence, were visualized significantly more often using this agent, so that patency, constriction, partial thrombosis or occlusion could be reliably diagnosed. Independent of the use of PGF, visualization of the confluence was improved by high CM doses in combination with high flow rates.