A cancer vaccine comprised of a synthetic peptide derived from the mucin 1 (MUC1) antigen with potential antineoplastic activity. Upon administration, MUC1 peptide vaccine may stimulate the host immune system to mount a cytotoxic T lymphocyte (CTL) response against tumor cells positive for the MUC1 antigen, resulting in decreased tumor growth. Overexpressed on many tumor cells, MUC1 antigen, a mammary-type apomucin, is a high-molecular-weight transmembrane glycoprotein.