To use embryonic stem (ES) cells in future therapeutical applications, differentiated hepatic phenotypes with specific liver functions would be necessary. We analyzed albumin (ALB), alpha-fetoprotein (AFP) and hepatic transcription factor (TF) gene expression in tissues derived from embryonic, fetal and adult liver, and compared the gene expression profiles with those from mouse ES cells after hepatic differentiation and from cultured adult hepatocytes. The mRNA expression of hepatocyte nuclear factor (HNF)-1alpha,beta, -3alpha,beta, -4alpha, -6, CCAAT/enhancer binding protein (C/EBP) alpha,beta, ALB and AFP relative to glyceralaldehyde-3-phosphate dehydrogenase (GAPDH) were studied by "real time" RT-PCR. ALBand AFP-expression was also determined by in situ hybridization (tissue) and immunofluorescence (ES-derived cells after hepatic differentiation, ES-HPC). Peak levels for HNF-1alpha, -3alpha, -4alpha and -6 were detected in early liver development at d9.5 and d11.5. C/EBPalpha and beta were most abundantly expressed in adult liver. ALB mRNA increased steadily from d10.5 on and was maximally present in adult liver. AFP was present at d9.5, peaked at d15.5 and dramatically declined in mature liver tissue. Based on immunofluorescence, ALB and AFP were expressed in approximately 20% of ES-HPC. While expression of HNF-3, 4 and 6 reached levels similar to adult hepatocytes, ALB and AFP expression was several orders of magnitude lowerthan in adult tissue or cells. Stages of liver organogenesis are characterized by specific expression patterns of developmentally regulated genes. With sophisticated differentiation protocols, hepatic gene expression can be induced in a proportion of ES cells with gene expression patterns similar to early fetal liver.