A peptide vaccine, containing human tumor-associated epithelial mucin (MUC1) conjugated with keyhole limpet hemocyanin (KLH), with potential antineoplastic activity. Vaccination with MUC1-KLH conjugate vaccine may stimulate humoral and cytotoxic T-lymphocyte (CTL) responses against tumor cells expressing the MUC1 antigen. In this vaccine, MUC1 antigen is conjugated with KLH, an immunostimulant and a hapten carrier, to enhance immune recognition. MUC1 antigen, a membrane-bound glycoprotein expressed by most glandular and ductal epithelial cells, is overexpressed in an aberrant or deglycosylated form in various cancers such as those of the breast, prostate, and ovary.