While the promise of harnessing the immune system for a therapeutic effect has remained largely unfulfilled for many years, the discovery of the central role of dendritic cells in stimulating antigen-specific immune responses has prompted new enthusiasm for immunotherapy of malignancies. Elucidation of the pathways of dendritic cell development and trafficking, acquisition and processing of antigen, and stimulation of T cells has suggested methods for generating and antigen-loading dendritic cells for use in immunotherapy protocols. Animal models have demonstrated that dendritic cells can stimulate protective antitumor responses in vivo. Phase I clinical trials have been initiated to address the safety and feasibility of immunizations with dendritic cells in humans with various malignancies.