Uncontrolled cell division is an indispensable event in tumor progression, and numerous molecules involved in this process have been the focus of intense investigation in tumor biology. Cyclins, molecules that orchestrate normal cell cycle progression, are abnormally overexpressed in various human cancers. We review evidence that the immune system recognizes some abnormally expressed cyclins as tumor antigens, such as cyclin B1, and we analyze the potential of cyclins D, E, and A to serve a similar function in cancer immunosurveillance.