18 cases of hepatosplenic schistosomiasis taken at random were studied. The transumbilical portal pressure, the trans-splenic portal pressure, the occluded thoracic duct pressure, and thoracic duct lymph flow were measured simultaneously before and after splenectomy. The findings were correlated with the clinical data, liver pathology, and operative findings. The transumbilical portal pressure-trans-splenic portal pressure gradient was found of significant importance. It was considered positive when the transumbilical portal pressure was higher than the trans-splenic portal pressure, in such cases the primary generating factor of portal hypertension is most probably of hepatic origin (post or presinusoidal obstruction; organic or functional). The gradient was considered negative when the transumbilical portal pressure was lower than the trans-splenic portal pressure; in such cases the primary generating factor of portal hypertension is most probably of splenic origin (hyperdynamic spleen) or in the portal vein (thrombosis). A significant correlation was found between the type of this gradient, the thoracic duct lymph flow and the clinico-pathological state. The thoracic duct flow was highest in the non-bleeders. Definite contrasting haemodynamic patterns were found between bleeders and non-bleeders. The bearing of these contrasting patterns on the selection of the operative procedure in the treatment of portal hypertension is suggested.