From 1 to 3% of acute renal failures are due to acute interstitial nephritis (AIN). Most of them are due to drugs. Nonsteroidal antiinflammatory drugs, penicillins and sulfonamides are the most frequently reported. Clinical presentation of drug-induced AIN has changed over time and with the use of new drugs. In fact actually the classic triad of fever, rash and eosinophilia is uncommon. Omeprazole is a drug widely used in the treatment of gastroesophageal reflux disease and peptic ulcer disease. Serious side effects are rare with this drug, but despite of its safety we can see serious adverse effects such as acute renal failure. We describe two cases of acute interstitial nephritis after use of omeprazole and a review of all the cases published in the last years.