In severe acute pancreatitis, multiple organ failure in the early stage after onset, and sepsis in the late stage, due to infection of pancreatic or peripancreatic devitalized tissue, contribute to its high mortality. In analogy with sepsis, evidence has accumulated of the significance of apoptotic cell death in the systemic manifestations associated with acute pancreatitis. Since we identified apoptosis-inducing activity in pancreatitis-associated ascitic fluid in 1995, a number of investigators, including our group, have reported, through animal experiments, that apoptosis occurred in the parenchymal cells constituting organs, such as alveolar epithelial cells in the lung, renal tubular cells in the kidney, and hepatocytes in the liver, and this apoptosis was involved in organ dysfunction with severe acute pancreatitis. Moreover, through clinical and experimental investigations, apoptosis has been revealed to be involved in the mechanism of infectious complications in acute pancreatitis. Namely, apoptosis in lymphatic tissues and peripherally circulating lymphocytes is involved in the impairment of cellular immunity, and apoptosis in gut epithelial cells is implicated in bacterial translocation. These results suggest that apoptotic cell death may play a considerable role in affecting mortality and morbidity in severe acute pancreatitis. Control of apoptosis could be a potent strategy for improvement of the clinical outcome in severe acute pancreatitis.