Abstract: Immature DCs were generated from the peripheral blood monocytes from five children with refractory solid tumors (Ewing sarcoma, synovial sarcoma, neuroblastoma) using GM-CSF and IL-4. These DCs were then pulsed with tumor-specific synthetic peptides or tumor lysates in the presence of the immunogenic protein KLH for 12 h. Pulsed DCs were administered subcutaneously every one or two weeks in an outpatient setting without any toxicity. In one patient with Ewing sarcoma, the residual tumor disappeared following autologous PBSCT and DC therapy, and a complete remission has been maintained for 77 months. In two patients with synovial sarcoma or with neuroblastoma, growth of the tumors was temporally suppressed for one and 10 months, respectively, followed by their exacerbation. A DTH response was detected against KLH in all five patients and against the tumor lysate in one patient. In the patients with a possible DC-mediated anti-tumor effect, the number of CD8+ HLA-DR+ lymphocytes and INF-γ+CD8+ lymphocytes increased and an elevation of the NK cell cytotoxic activity was observed during and/or after DC therapy. DC-based immunotherapy may therefore be a feasible, well-tolerated and promising approach in the treatment of children with refractory malignant tumors.