A cancer peptide vaccine comprised of four peptides derived from the tumor-associated antigen (TAA) HER-2/neu (ErbB-2), with potential immunomodulating and antineoplastic activities. Upon administration of the multi-epitope HER2 peptide vaccine TPIV100, the four peptides may induce a cytotoxic T-lymphocyte (CTL)-mediated immune response against tumor cells expressing the HER-2/neu antigen, which may result in the inhibition of proliferation in Her-2/neu-expressing tumor cells. Her-2/neu, a member of the epidermal growth factor receptor (EGFR) family of tyrosine kinases, is overexpressed in various tumor cell types. To enhance immunity, the peptides are admixed with the adjuvant granulocyte macrophage-colony-stimulating factor (GM-CSF).