We attempted to find a specific antigen of oral squamous cell carcinoma (SCC) cells that could be safely applied to gene therapy in the conservative clinical treatment of oral cancer. We performed subtraction using normal human keratinocyte cells, followed by selection using four oral SCC cell lines. We isolated three clones from poorly differentiated SCC cells and four from well-differentiated SCC cells. These seven clones adsorbed to the oral SCC cells at rates 10-100 times those of normal human keratinocyte cells. The three clones from the poorly differentiated SCC cells showed the same peptide sequence (LAPRTHP). Of the four clones from the well-differentiated SCC cells, three showed the same peptide sequence (FGTLPGT) and the fourth showed a different one (VTPNSTP). Each peptide sequence may recognize the material that exists specifically on the oral SCC cell cortex. We can expect applications not only for tumor-targeting treatment using a gene therapy virus vector but also for diagnosis using, as a tumor marker, the peculiar SCC surface material that these peptides recognize.