While the relative incidence of serious nephrotoxicities in the population consuming nonsteroidal anti-inflammatory drugs (NSAIDs) is very low, the frequency of adverse events in patients at risk has considerably increased due to the rising popularity of the use of the drugs in recent years. Under normal conditions, NSAIDs have relatively little effect on the kidney because of low renal production of prostaglandins. However, in the presence of renal hypoperfusion in which local synthesis of vasodilator prostaglandins is increased to protect the glomerular hemodynamics and to maintain appropriate renal tubular transport of fluid and electrolytes, inhibition of prostaglandin synthesis by NSAIDs can lead to vasoconstrictive acute renal failure as well as fluid and electrolyte disorders such as sodium retention and resistance to diuretics, hyponatremia and hyperkalemia. Conditions that increase the risk for NSAID-induced nephrotoxicities include volume depletion from diuretics and other causes, edematous states such as congestive heart failure and cirrhosis of the liver, old age and underlying renal disease, especially in the presence of renal functional impairment. In addition, renal parenchymal diseases may develop in susceptible patients taking NSAIDs. These include acute tubulointerstitial nephritis, frequently associated with nephrotic syndrome, and chronic progressive renal disease, with or without renal papillary necrosis. Rare cases of vasculitis and glomerulonephritis have also been reported. Finally, NSAIDs may aggravate hypertension by interacting with antihypertensive drugs, especially with diuretics and beta-blockers. Withdrawal of NSAIDs in patients at risk can frequently reverse or improve the nephrotoxicities. It is recommended that physicians be aware of the clinical settings that increase the risk for NSAID-induced nephrotoxicities and take preventive or therapeutic measures accordingly.