Tissue-specific tumorigenesis can be induced in transgenic mice by the directed expression of SV40 large T antigen. In an attempt to induce the tumors or cancers in stomach tissues, nine transgenic mice were genrated that harbored a chimeric gene composed of the SV40 large T antigen gene fused to the exon II of a human gastrin gene including 5 and 3 flanking sequences- It was represented through germ-line transmission that three transgene mice were mosaic. The transgene was expressed in all tissues examined by reverse transcription DNA polymerase chain reaction (RT-PCR) whereas endogenous mouse gastrin transcripts were detected only in both stomach and brain tissues of the transgenic mouse. The antral region of transgenic mice (TEX-3 line) exhibited abnormal state in appearance although stomach sections of transgenic mice have yet to show any histological or pathological changes.