A report of a probable case of acute, reversible renal failure and hyperkalemia, after an increase in dose of ibuprofen, is presented. Other cases of renal dysfunction associated with various nonsteroidal antiinflammatory drugs (NSAIDs) are reviewed. The ability of NSAIDs to inhibit prostaglandin synthesis may explain the various renal consequences. Possible predisposing factors to renal deterioration include the amount of drug consumed, presence of compromised renal blood flow, underlying renal insufficiency, nephrotoxic drug combinations, and high urinary prostaglandin excretion. Generally, the renal failure with NSAIDs is acute and reversible, though analgesic nephropathy with papillary necrosis and chronic renal failure are reported. Electrolytes, blood urea nitrogen, and serum creatinine levels need to be monitored in high-risk patients with predisposing factors and for chronic, long-term use of drugs that inhibit prostaglandin synthesis.