Since 1970, we have been trying to culture cells of human hepatoma, hepatoblastoma and human embryonic liver for the purpose of researching the nature of human liver cells and related diseases. In our laboratory we succeeded in establish 2 cell lines from hepatoma (HLE and HLF) in 1975 and a cell line from human hepatoblastoma (HUH-6) in 1976. Then we tried to culture from human embryonic liver. We could not establish an epithelial cell line from human embryonic liver, but could obtain three epithelioid cell lines and got some important results. The results are summarized as follows. 1. The most important condition to maintain the epithelial cell of liver alive in vitro is the age of embryo and freshness of it: the older the embryo, the better condition we got, and the fresher, the better. 2. We have tried many growth media to find the selective growth of liver epithelial cell in vitro and succeeded in obtaining media suitable, not completely but satisfactory, for maintenance of epithelial cells. The media we got were LD + Glutamine and RPMI 1640 + Lactalbumin. 3. Bovine serum is suitable for the maintenance of liver epithelial cell and human serum showed marked cytotoxic effect on cell growth. 4. Inoculum cell number of living large granular hepatocytes from 2 to 10 × 10(4)/ml showed good maintenance of epithelial cells in vitro for 60 days. 5. We could recognize 5 kinds of cells under phase contrast microscope and cover-slip examination. i. Large granular hepatocytes (mature type of liver epithelial cell). ii. Small agranular epithelial cells (immature type of liver epithelial cell). iii. Fibroblasts. iv. Endothelial epithelium (Kupffer's cell). v. Hematopoietic cells due to extramedullary hematopoesis. 6. Marked proliferation of mesenchymal cells were observed.