Proteolytic enzymes, lipase, kinins, and other active peptides liberated from the inflamed pancreas convert inflammation of the pancreas, a single-organ disease of the retroperitoneum, to a multisystem disease. Adult respiratory distress syndrome, in addition to being secondary to microvascular thrombosis, may be the result of active phospholipase A (lecithinase), which digests lecithin, a major component of surfactant. Myocardial depression and shock are suspected to be secondary to vasoactive peptides and a myocardial depressant factor. Coagulation abnormalities may range from scattered intravascular thrombosis to severe disseminated intravascular coagulation. Acute renal failure has been explained on the basis of hypovolemia and hypotension. The renin-angiotensin alterations in acute pancreatitis (AP) as mediators of renal failure need to be studied. Metabolic complications include hypocalcemia, hyperlipemia, hyperglycemia, hypoglycemia, and diabetic ketoacidosis, of which hypocalcemia has been long recognized as an indicator of poor prognosis. The pathogenesis of hypocalcemia is multifactorial and includes calcium-soap formation, hormonal imbalances (e.g., parathyroid hormone, calcitonin, glucagon), binding of calcium by free fatty acid-albumin complexes, and intracellular translocation of calcium. Subcutaneous fat necrosis, arthritis, and Purtscher's retinopathy are rare. The various prognostic criteria of AP and other associated laboratory abnormalities are manifestations of systemic effects. Early recognition and appropriated management of these complications have resulted in improved prognosis of severe AP.