Drug-induced renal disease is a common problem. Drugs cause several renal syndromes, such as prerenal azotemia, fluid and electrolyte abnormalities, acute tubular necrosis, acute interstitial nephritis, and chronic interstitial nephritis. Acute renal failure due to acute tubular necrosis is the most common syndrome and is most frequently caused by aminoglycoside antibiotics, radiographic contrast agents, and amphotericin B. Avoidance of these drugs in volume-depleted or hypotensive patients with preexisting renal disease or in those receiving multiple nephrotoxic drugs is the most effective way to reduce nephrotoxicity. Acute interstitial nephritis is an immune process that is most commonly caused by penicillins, diuretics, allopurinol, nonsteroidal anti-inflammatory drugs, cimetidine, and sulfonamides. Prompt recognition of the disease and cessation of the responsible drug are usually the only necessary therapy. Chronic interstitial nephritis is most often seen after prolonged use of several different types of analgesic agents, including aspirin, acetaminophen, and nonsteroidal anti-inflammatory drugs. These patients develop recurrent papillary necrosis and eventually chronic renal failure. They are also at risk of developing transitional cell carcinomas of the urinary collecting system. Some patients who are receiving cyclosporine also develop chronic renal failure due to interstitial fibrosis.