Dendritic cells (DCs) represent a group of antigen-presenting leukocytes which are very effective in activating resting T-cells. DCs are present in almost all tissues of the body, but they are generally difficult to isolate. The study of human DCs has recently become greatly facilitated due to the advent of methods for isolation and in vivo generation of DCs from blood. Experiments in animal models have shown that DCs loaded with tumour antigens may induce effective immune responses against cancer. Now the potential of vaccination with tumour antigens presented on DCs is being evaluated in cancer patients. Preliminary clinical studies have shown encouraging results.