Dendritic cells (DCs) initiate and direct the immune response. Their inability to detect danger signals from transformed cells and to generate an effective immunological response may allow cells with a malignant phenotype to evolve into cancers. This defect can be corrected for many cancer types and the immune response boosted to eliminate malignant cells by means of DC-based vaccines/therapies. Rapid advances in our understanding of basic DC physiology and improved methods for DC isolation have made clinical application of DC therapy practical, and encouraging phase I/II results are emerging.