Apoptosis plays an important role in development and maintenance of tissue homeostasis. Intensive efforts have been made to explore the molecular mechanisms of the apoptotic signaling pathways including the initiation, mediation, execution and regulation of apoptosis. Caspases are central effectors of apoptosis. Cells undergo apoptosis through two major pathways, namely the extrinsic pathway (death receptor pathway) or the intrinsic pathway (the mitochondrial pathway). Finally, the contents of dead cells are packaged into apoptotic bodies, which are recognized by neighboring cells or macrophages and cleared by phagocytosis. Cellular apoptosis is tightly controlled by a complex regulatory networks including balancing pro-survival signals. De-regulation of apoptosis may lead to pathological disorders such as developmental defects, autoimmune diseases, neurodegeneration or cancer. Increasing attention is being focused on alternative signaling pathways leading to cell death including necrosis, autophagy, and mitotic catastrophe. Understanding of cell death signaling pathways is relevant to understanding cancer and to developing more effective therapeutics.