Publisher Summary This chapter reviews the information available about apoptosis and assesses its potential use to enhance the efficacy of radiation therapy. There are two different avenues through which augmentation of apoptosis might improve cancer therapy. As cancer cells may die by apoptotic processes after exposure to radiation, targeting the apoptotic process might be expected to alter therapeutic success. It is possible to greatly enhance the death of the cancer cells after exposure to therapeutic agents. It is also possible to contemplate therapies that might directly induce apoptosis in tumor cells without the application of toxic agents. The application of various hormonal agents or blockage of autocrine growth factor loops is also included. The chapter discusses the induction of apoptosis in cancer cells by therapeutic agents, especially ionizing radiation, and describes some of the genetic mechanisms known to control that induction and their link to cell proliferation. However, the manipulation of apoptosis or of cellular proliferation checkpoints will affect survival of tumor cells after treatment with toxic agents such as radiation.