Prostaglandins play an important role in the regulation of renal hemodynamics and sodium excretion. Thus, the administration of non-steroidal anti-inflammatory drugs (NSAIDs) induces a renal vasoconstriction and sodium and potassium retention. In some high risk patients, this may lead to acute renal failure. The anti-inflammatory and renal effects of conventional NSAIDs are mediated by the non-selective inhibition of two cyclo-oxygenases, COX-1 and COX-2. Recently, highly selective COX-2 inhibitors have been developed such as celecoxib (Celebrex) and rofecoxib (Vioxx). These drugs were designed to preserve the analgesic and anti-inflammatory properties of NSAIDs while reducing their gastro-intestinal and renal side effects. Selective COX-2 inhibitors have indeed less gastro-intestinal side-effects. However, their renal profile is comparable to that of non-selective inhibitors as they induce a decrease in glomerular filtration rate and a sodium and potassium retention. Thus, despite the good gastro-intestinal safety profile of selective COX-2, one should be careful with the use of these agents in high risk patients as they may induce similar renal complications as non-selective NSAIDs.