Despite rapid advances in cancer therapeutics, relapsed disease due to failed immunosurveillance remains a major problem in many cancers. Dendritic cells are recognized as key to the induction of immune responses to cancer and intensive study is underway to facilitate their use in cancer immunotherapy. In initial clinical trials, dendritic cell preparations were, with the benefit of hindsight, largely sub-optimal, yet encouraging results have been seen. The challenge now is to expand our knowledge of the interactions between tumors and the immune system, through basic scientific research and coordinated large-scale clinical studies. This review focuses on the anti-tumor immune response, human dendritic cell biology and the results of recent clinical studies of dendritic cell immunotherapy for cancer.