Tumour immunotherapy using dendritic cells (DCs) is a new therapeutic approach, which has been applied to a variety of different cancers over the last 5 years. Here we discuss the clinical results of these trials in relation to the different protocols used to generate DCs, and in particular the effect that DC maturation state has had on clinical responses. In ten different melanoma trials a total of 167 patients have been treated, resulting in 9 complete tumour regressions, 24 partial regressions, 26 patients with stable disease, and 108 with progressive disease. Favourable response, defined as any outcome other than progressive disease, was not associated with previous chemotherapy, but was significantly correlated ( p<0.001) with the addition of TNF-alpha for the maturation of DCs in vitro. Hence DC maturation state has had an impact on clinical responses to therapy. However, TNF-alpha is not the only molecule capable of inducing DC maturation, and strategies for improving clinical responses by optimizing DC maturation are discussed.