Human fetal liver (HFL) cell culture was initiated from a pool of six normal human liver tissues. The proliferation and viability of HFL cells were evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay, and the cells increased by more than 100-fold by culture for 15 d. The levels of expression of albumin (ALB), hepatocyte nuclear factor 4alpha, hepatocyte growth factor, CYP3A4, CYP3A5, and CYP3A7 mRNAs in HFL cells increased with culture period, while that of alpha-fetoprotein (AFP) mRNA decreased gradually. In HepG2 cells, however, the expression levels of ALB and AFP mRNAs were not changed, and the levels of expression of CYP3A4, CYP3A5, and CYP3A7 mRNAs decreased gradually. The mRNA expression of major CYP isoforms including CYP3As, i.e., CYP1A2, CYP2A6, CYP2B6, CYP2C (2C9 and 2C19), CYP2D6, and CYP2E1, could be detected in HepG2 cells. With the exception of CYP1A2, all of the CYP mRNAs expressed in HepG2 cells were detected in HFL cells. In HFL cells, CYP3A4 and CYP3A7 mRNA expression levels were markedly up-regulated by dexamethasone (DEX), but not by rifampicin (RIF). CYP3A5 mRNA expression was increased to a level 3-fold greater than control by DEX. On the other hand, CYP3A4, CYP3A5, and CYP3A7 mRNA expression levels in HepG2 cells were increased from 2- to 3-fold by treatment with DEX and RIF. Pregnane X receptor mRNA was expressed in HepG2 cells, but not HFL cells. These results indicate that the character of HFL cells with regard to CYP expression was different from that of HepG2 cells.