The expression plasmid PCEA-TK or pCEA-CD was constructed by ligating the CEA gene promoter to suicide gene such as HSV-TK (herpes simplex virus thymidine kinase) gene or EC-CD (E. coli cytosine deaminase) gene. A human colorectal carcinoma cell line LoVo or a human uterine cervical cancer cell line HeLa was co-transfected with pSV2-neo and PCEA-TK (or PCEA-CD). After selection with G418, the transgenetic cell clones (hoVo/CEA-TK,LoVo/CEA-CD, HeLa/CEA-TK and HeLa/CEA-CD) were obtained. There was no significant difference in either morphology or cell growth curve between suicide gene transduced cells and wild type cells. But LoVo/CEA-TK (or LoVo/CEA-CD) cells were 2000(or 700) times more sensitive to the cytotoxicity of prodrug ganciclovir(or S-Fluorocytosine)than parental LoVo cells. However, HeLa/CEA-TK or HeLa/CEA-CD cells were still resistant to Ganciclovir (or 5-Fluorocytosine). These results showed the possibility of gene therapy for human colorectal carcinoma by cell type-specific expression of suicide genes.