Basic and clinical investigators systematically compile a comprehensive but concise summary of essential, up-to-date information about apoptosis. The authors present the concepts, the molecular architecture, the biochemical pathways, and the pathophysiological significance of apoptosis. In addition, standard biochemical and cell biologic approaches to apoptosis research are described as a guideline for bench work, with clinical applications detailed for immune disorders, cancer, ischemia/reperfusion injury, and neuronal degeneration.