Heat shock proteins (HSPs) are associated in vivo with the entire repertoire of peptides (antigenic and otherwise) generated within that cell. Immunization with such non-covalent HSP-peptide complexes is unusually efficient in eliciting cellular immune responses against the antigenic peptides associated with the HSPs. This broad and general principle is the basis for a new generation of vaccines against cancers and infectious diseases and circumvents the need for identification of the T-cell epitopes for any given cancer or infectious agent.