Inoperable adenocarcinoma in colon or lung shows resistance to conventional anti-cancer therapy. For these cancers, the feasibility of transcriptionally targeted killing of carcinoembryonic antigen (CEA)-producing adenocarcinoma cells was investigated. Adenovirus vectors carrying a CEA promoter to express E. coli lacZ (AdCEALacZ) or herpes simplex thymidine kinase (AdCEATK) were made and their in vitro and in vivo tumoricidal effects on CEA-producing or non-producing colon and lung cancer cells were evaluated. In vitro infection with AdCEALacZ showed significantly higher CEA promoter-driven lacZ expression in CEA-producing adenocarcinoma cells including VMRC-LCD and LoVo than in CEA-non-producing cells. AdCEATK-infected LoVo showed higher sensitivity to ganciclovir than control vector-infected LoVo or AdCEATK-infected HeLa both in vitro and in subcutaneously implanted tumors of nude mice. Moreover, total tumor elimination in vivo was achieved by either pre-infection of as few as 30% of cells comprising tumors or by direct in vivo injection of AdCEATK to pre-established LoVo tumors. In addition, CEA promoter-driven lacZ expression in LoVo cells was enhanced by the addition of interleukin-6 (IL-6) in vitro. These results provide a rationale for CEA-promoter-driven, adenovirus-mediated gene therapy for CEA-producing adenocarcinomas in colon and lung with reduced toxicity to normal cells.