During the last decade use of dendritic cells (DC) has moved from murine and in vitro studies to clinical trials as adjuvant in cancer immunotherapy. Here they function as delivery vehicles for exogenous tumor antigens, promoting an efficient antigen presentation. The development of protocols for large-scale generation of dendritic cells for clinical applications has made possible phase I/II studies designed to analyze the toxicity, feasibility and efficacy of this approach. In clinical trials, DC-based vaccination of patients with advanced cancer has in many cases led to immunity and in selected patients to tumor regression. However, the majority of clinical trials are still in phase I, and interpretations are hampered by pronounced variation in study design related to technical aspects of DC preparation, treatment and schedule, monitoring of immune response, and clinically relevant endpoints, including toxicity and response evaluation. This paper aims to review the technical aspects and clinical impact of vaccination trials, focusing on the generation of DC-based vaccines, evaluation of immunologic parameters and design of clinical trials necessary to meet the need for good laboratory and clinical practice.