AIMS--To evaluate the role of bilharzial hepatic fibrosis--whether pure or combined with chronic hepatitis B virus infection--on the functional activity of vitamin K dependent coagulation proteins. METHODS--Coagulation screening using prothrombin time (PT), partial thromboplastin time (PTT), and thrombin time (TT) was carried out on 31 patients with endemic Egyptian hepatosplenomegaly and on 14 healthy controls. The functional activities of factors II, VII, IX and X and protein C were measured. Patients were classified as pure hepatosplenic schistosomiasis (n = 17) and schistosomiasis with concomitant chronic hepatitis B virus infection (n = 14). RESULTS--Prolongation of the PT and PTT were noticed in bilharzial patients compared with the controls. The increase in the TT remained within the upper range of normal. Factors II, VII, IX and X and protein C functional activities were significantly reduced in all groups studied. CONCLUSION--The decreased activity of vitamin K dependent coagulation factors might be partially offset by the reduced activity of circulating protein C which tends to establish a haemostatic balance at a lower level in endemic Egyptian hepatosplenomegaly. No significant difference could be shown between the pure and mixed cases. Schistosomal coagulopathy is therefore not necessarily aggravated by chronic hepatitis B virus infection.