Apoptosis or programmed cell death (PCD) is a physiological process critical for organ development, tissue homeostasis and elimination of defective or potentially dangerous cells in complex organisms. Apoptosis permits cell death without a concomitant inflammatory response in the surrounding tissues. The process of apoptosis depends on the reception of multiple extracellular and intracellular signals, integration and amplification of these signals by second messengers and finally, activation of the death effector proteases. Defects in control of apoptotic pathways may contribute to a variety of diseases including cancer, autoimmune and neurodegenerative conditions and AIDS. While many components of the regulatory network controlling apoptosis have been defined, the mechanisms of action and patterns of interaction of these factors remain controversial. This article summarizes some of the known aspects of signaling pathways involved in apoptosis.