Alpha-fetoprotein (AFP) is a specific tumor marker for hepatocellular carcinoma (HCC). A gene expression system under AFP promoter/enhancer control would be specific for AFP producing cells, but its low expression level is a problem which must be overcome. For the purpose of AFP promoter enhancement, we constructed two recombinant adenoviral vectors; one containing the AFP promoter domain and transcriptional activator VP16LexA, and another the transcriptional activator binding site, the AFP promoter and the Cre gene. The lacZ gene was transduced and expression of beta-galactosidase was estimated in vitro. We achieved a 3-fold enhancement of gene expression compared with previous transfection of the transcriptional activator gene into AFP producing cells, and 57 to 330-fold higher cell type specificity was maintained as compared with an ordinary gene expression system. This AFP-producing cell specific gene transduction, employing our enhanced gene expression method, may contribute to targeting gene therapies with a variety of vectors.