Acute interstitial nephritis (AIN) is a form of inflammatory renal disease affecting predominantly the tubules and the interstitium. Drugs, particularly beta-lactam antibiotics and non-steroidal anti-inflammatory drugs, are currently the most common causes. The pathogenesis of drug-induced AIN is complex but there is good clinical evidence for an immune-mediated reaction. Clinical findings may be variable depending on the drug involved and the individual response. Most patients recover from the acute renal failure; however, in older patients or in patients with pre-existing renal insufficiency the recovery of renal function may be incomplete.