Recent progress in the approach towards immunotherapy of cancer consists in molecular definition of tumor antigens, new tools for phenotypical and functional characterization of tumor-specific effector cells and clinical use of novel adjuvants for optimal stimulation of a cancer-specific immune response such as dendritic cells. In spite of these advances and immunological as well as clinical responses in selected patients, mechanisms involved in dendritic-cell-based cancer immunotherapy are still poorly understood. Therefore, a standardized study design and small pilot trials are needed to explore open scientific questions in future clinical trials. This review focuses on the different parameters of dendritic cell biology relevant to cancer immunotherapy and on innovative approaches to hopefully enhance the efficacy of dendritic cell vaccination.