The preceding chapters in these two volumes on tumor suppressor genes (TSG) are a comprehensive compilation of what is currently known about the structure, function, activation, and regulation of TSGs, along with the roles they play in the myriad biochemical pathways that network to result in living cells. With recent developments in molecular genetics, new information is revealed daily, and it is likely that we have only scratched the surface of the base of knowledge about TSGs that will soon be available. Even so, the studies reported thus far have already led to the identification of genetic alterations in TSGs that are responsible, in whole or in part, for cancer, and subsequently to the development and implementation of formidable therapeutic strategies.