In order to determine the usefulness value of the antibodies to cytokeratins (CK) of "bile duct type" in the differential diagnosis between hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CC), we have made an immunocytochemical investigation, using the antibodies specifically recognizing CK19 and CKIS, seperately, in liver, and laminin (LN) antibody. All the CC examined (10 cases) were found CK19-positive; interestingly, CK19-positive cancer cells were also observed in 38% of HCCs (14137). Therefore, CKI9 was not a reliable marker in differentiating HCC from CC, in our consideration. The CK19 expression in HCC was showed to be irrelevant to their differentiation degree, but related to the histologic subtypes which indicated the directions of their differentiation. CKI9 expression was observed in all the HCC cell nests with glandular differentiation, and an uncontinuous LN-positive basement membrane-like structure was immunolocalized around these cells, which indicated that the glandular differentiation and CK19 expression in HCC were also related to the LN deposition, as in fetal liver and some chronic liver disorders.