It is now clear that many human tumour antigens can be recognised by the immune system. These tumour antigens can be classified into several groups including cancer-testis, differentiation, tissue specific, over-expressed, and viral-associated antigens. In many cases, there is a known molecular basis of carcinogenesis which provides the explanation for the differentiated expression of these antigens in tumours compared with normal cells. Improved understanding of the biology of the immune response, particularly of immune recognition and activation of T-cells, allow better design of vaccines. Pre-clinical comparative studies allow evaluation of optimal vaccine strategies which can then be delivered to the clinic. Currently, a range of cancer vaccines are being tested including those using tumour cells, proteins, peptides, viral vectors, DNA or dendritic cells. Ultimately, this research should give rise to an entirely new modality of cancer treatments.