Emerging evidence indicates that apoptosis is regulated by some of the same signal transduction pathways previously implicated in other physiological cellular responses, including alterations in intracellular Ca2+ compartmentalization, activation of protein kinases and phosphatases, alteratios in pH and oxidative stress. Interestingly, signals that promote apoptosis in one model can suppress cell death in another, indicating that cellular responses are determined by the intrinsic programming of the cell in question. This review will summarize current knowledge of the signal transduction pathways regulating apoptosis and discuss how they may be coupled to components of the molecular machinery for cell death.