Cancer vaccines need to be designed to effectively induce tumor-specific CD8(+) T cells, the key effector cells in immune responses against tumors. These T cells recognize peptides generated from cellular proteins by limited proteolysis, and bound and presented at cell surfaces by MHC class I molecules. Mimotopes, mimetics of T cell epitopes, have been derived from known epitopes by sequence modification, or developed de novo using combinatorial peptide libraries to scan the entire sequence space for peptides that induce the desired T cell responses. Mimotopes of both types have been tested in clinical vaccination trials for treatment of cancer.