The localization of fibronectin (FN) in human hepatocellular carcinoma (HCC) was studied in thirty‐six HCC tumors (19 autopsy and 17 surgical specimens), two xenografted tumors of HCC to BALB/c mice and three HCC cell lines. The synthesis of FN was also examined in three HCC cell lines. FN was demonstrated on the endothelial surface of the blood spaces of cancerous tissue. Cytoplasmic and intercellular localization of FN was also observed. But there was no correlation between the localization pattern of FN and metastasis. In the two xenografted HCC tumors, FN was found in association with the blood vessels of the tumor tissue and between the HCC tumor cells. In all 3 HCC cell lines, FN was localized on the surface and in the cytoplasm of some HCC cells. FN was detected in the serum‐free culture media of three HCC cell lines by immunoelectroblotting. The electrophoretic pattern of FN synthesized by these cell lines was different from that of plasma‐FN and resembled that of cellular‐FN synthesized by normal liver fibroblasts.