The prostaglandins are a series of fatty acid products derived from the cellular metabolism of arachidonic acid. The kidney makes prostaglandins and the endogenous renal prostaglandins appear to play a role in the regulation of renal hemodynamics, renal salt and water excretion, and control of the level of activity of the renin-angiotensin system. The administration of nonsteroidal anti-inflammatory drugs blocks cyclooxygenase activity, an early step in the synthesis of prostaglandins. This class of drugs, under certain circumstances, leads to sodium retention, hyperkalemia and several different forms of acute and chronic renal failure. The potential role of altered prostaglandin synthesis in leading to these clinical syndromes is reviewed.