Research over the last decade has demonstrated that human tumors are immunogenic and that cancer patients can have immune responses specific for their tumors. At the same time, many mechanisms have been identified that act to limit the tumor specific immune response. Cancer vaccines may have the potential to stimulate tumor immunity to levels that have an impact on tumor growth. The development and testing of cancer vaccines may lead someday to the ability to use the immune system to prevent the first development of cancer or of relapse in patients who have been previously treated. From the Series:Science Forum