Immunotherapy is in principle attractive, as it exploits the immune system's own method of recognizing and destroying tumours. Tumour cells express a number of mutated or over-expressed antigens, which make it possible for the immune system to distinguish between tumour cells and normal cells. Cancer vaccines use tumour-associated antigens to stimulate the patient's immune cells. In the clinical setting, individual differences between cancer patients is of vital importance, as the majority of tumour antigens may be unique to each individual. Genetic differences in patients' immune systems also suggest the need for individualised vaccines. This article gives a short introduction to the basic principles of tumour immunology and development of cancer vaccines. Clinical trials with emphasis on those with peptide and dendritic cell vaccines are presented, and the future development of cancer vaccines is discussed. A number of trials have shown tumour-specific immune responses and demonstrated that side-effects are generally not a problem. Limited documentation is available for the clinical effects. It is important to establish why some immune responses appear to give tumour regression while others are without clinical importance.