Clinicoradiological features were studied in 20 patients with 22 mass lesions of combined hepatocellular carcinoma and cholangiocarcinomas and findings of computed tomography in 12 of these patients with 14 hepatocellular carcinoma-cholangiocarcinomas. Five of these patients also had single overt hepatocellular carcinomas. The incidence of hepatocellular carcinoma-cholangiocarcinoma was 3.3% among the patients with primary liver cancer treated in our hospital. HBsAg was present in 25%, and increased levels of serum alpha-fetoprotein (> 200 ng/ml) and carcinoembryonic antigen (> 5 ng/ml) were found in 25% and in 47%, respectively. Associated cirrhosis was present in 60%. Analysis of 14 hepatocellular carcinoma-cholangiocarcinomas in 12 patients in whom the enhancement pattern on dynamic computed tomography and pathological findings could be studied and compared suggested three tumor types. Nine lesions (type A) were demonstrated only as areas with high-density peripheries in the early phase of enhancement that evolved into a pattern of peripheral low density and central high density in the late phase. Four masses (type B) were shown as hyperdense tumors (early phase) that changed to low density in the late phase. One mass (type C) was seen as a low-density lesion that did not change. Histopathologically, type A comprised hepatocellular carcinoma-predominant components in the peripheral area, cholangiocarcinoma-predominant components with abundant fibrous stroma in the central area and a tissue transitional between the two in the midzone. By contrast, two of four type B masses comprised hepatocellular carcinoma with scattered cholangiocarcinoma components throughout the tumor.(ABSTRACT TRUNCATED AT 250 WORDS)