A cancer vaccine containing HLA class I- and II-binding peptides derived from the NY-ESO-1/LAGE-1 cancer/testis antigen with potential immunostimulatory and antineoplastic activities. Upon administration, NY-ESO-1/LAGE-1 HLA class I/II peptide vaccine may induce a cytotoxic immune response against tumor cells that over-express NY-ESO-1/LAGE-1. Rarely expressed by normal cells, the NY-ESO-1/LAGE-1 cancer/testis antigen has been shown to be preferentially expressed on the surface of some cancer cell types.