Nonsteroidal anti-inflammatory drugs are well-known culprits in the development of acute renal insufficiency in high-risk patients. The recent release of the selective cyclooxygenase-2 enzyme inhibitors for the treatment of inflammatory diseases and pain syndromes has been associated with a clear-cut decrease in adverse gastrointestinal effects. However, the nephrotoxic potential of these agents in patients with prostaglandin-dependent states and chronic renal impairment is unknown. Many clinicians commonly wonder if these agents can be safely prescribed to such high-risk patients. We present two cases of acute renal failure complicating the course of therapy with celecoxib in patients with chronic renal insufficiency.