Mutant ras oncogene peptides may induce specific anti-ras cellular immune responses in vaccinated patients. Moreover, a human CD8+ CTL epitope(s) reflecting a specific point mutation in the K-ras oncogene at codon 12 was identified. The mutant ras peptide has implications for both active and passive immunotherapies in selected carcinoma patients. A nested 10-mer peptide was identified [i.e., ras5-14(Asp12)], which was shown to bind to HLA-A2 and display specific functional capacity for expansion of the in-vivo-primed CD8+ CTL precursors.