The cellular distribution of tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 was studied by using in situ hybridization in surgically removed human hepatocellular carcinomas (HCCs) and cholangiocellular carcinomas (CCCs). The purpose of this study was to characterize the protein involvement of TIMPs in the development of HCCs and CCCs. All HCCs and CCCs expressed TIMPs. The distribution of transcripts for TIMPs in the tumors was mostly homogeneous. Expression of TIMP in cancer cells was more intense than that in the surrounding noncancerous liver (either, cirrhosis, chronic hepatitis, or normal), and expression of TIMP-1 was stronger than that of TIMP-2. Expression of TIMPs varied among HCC nodules, but there was no obvious association between the expression level of TIMPs and differentiation stages or invasiveness of the HCCs. Transcripts for TIMPs were clearly demonstrated in the metastatic HCC nodules in the lung. Expression of TIMP-1 CCC was strong, and small nodules of CCC were recognized in the liver. Immunohistochemical study for TIMP-1 revealed a consistent staining of the TIMP protein with the transcripts. In the peritumoral histologically normal liver, which was not infected with either hepatitis B or C virus, expression of TIMP-1 was found in various cell types, but that of TIMP-2 was weak. Expression of TIMP-1 in hepatocytes revealed clear zonal distribution. These results suggest that TIMPs may act on modulating the matrix/tumor interaction and may play an important role in growth and invasion of HCCs and CCCs. Expression of TIMP-1 can be a marker of HCC metastasis to the lung, and also that of the extent of CCC invasion. Furthermore, the consistent expression of TIMPs in many cell types of the noncancerous liver suggests some unknown functional role that must be clarified.