The ability of heat shock proteins to chaperone peptides, including antigenic peptides; to interact with antigen-presenting cells through a receptor; to stimulate antigen-presenting cells to secrete inflammatory cytokines; and to mediate maturation of dendritic cells makes them a unique starting point for generation of immune responses. These properties also permit the utilization of heat shock proteins for development of a new generation of prophylactic and therapeutic vaccines against cancers and infectious diseases.