Dendritic cells (DCs) are potent antigen-presenting cells that have the ability to stimulate primary T cell antitumor immune responses in animals and humans. Since the first published clinical trial of dendritic cell vaccination in 1995, 98 studies describing more than 1000 vaccinees have been published in peer-reviewed medical journals or presented at the annual meetings of the American Society for Clinical Oncology, the American Association of Cancer Research, or the American Society of Hematology. Trials have been performed in 15 countries. Trials included patients with more than two dozen tumor types; most trials studied patients with malignant melanoma, prostate cancer, colorectal carcinoma, or multiple myeloma, using autologous DCs pulsed with synthetic antigens or idiotype antibodies. The DC vaccines were also prepared by pulsing DCs with tumor lysates or RNA, by transfection with tumor DNA, or by creating tumor cell/DC fusions. Various approaches to vaccine cell numbers, length of vaccine program, site of vaccination, frozen preservation of vaccine, and use of a maturations step for DCs were used. Adverse effects associated with DC vaccination were uncommon; most were mild and self-limited and none were serious. Clinical responses were observed in approximately half the trials. The DC vaccination may provide a safe approach to cancer immunotherapy that can overcome the limited reach and immunogenicity of peptide vaccines.