Apoptosis is type of cell death that is highly regulated and critically important for maintaining homeostatic cell numbers. Disruption of normal cell death mechanisms contributes to the pathogenesis of some diseases, including cancer. Expression of oncogenes, such asbcl-2and inactivation of tumor suppressor genes, such asp53, reduce the susceptibility of cells to undergo apoptosis. Methods have recently been established that enable rates of apoptosis to be rapidly and reliably quantitated in routinely acquired patient tissue samples. The determination of the susceptibility of individual malignancies to undergo apoptosis in response to therapy may provide useful information for predicting patient response and for the design of more effective treatment strategies.