Non-narcotic analgesics have acute and chronic effects on the kidney. Until quite recently chronic effects have received much more attention than acute effects. Renal papillary necrosis attributed to prolonged intake of analgesic compounds was first described from Switzerland in the 1950s, and subsequently in many countries including Scandinavia, Australia, Belgium and Canada. Renal papillary necrosis is now accepted as an effect of over-the-counter analgesic compounds and has also been recorded with many individual non-steroidal anti-inflammatory drugs (NSAIDs). Evidence suggests that uroepithelial tumours also occur as a complication of prolonged abuse of analgesic compounds. Clinical evidence associating renal papillary necrosis with compound analgesics and NSAIDs has been backed up by experimental evidence showing that these drugs cause renal papillary necrosis in animals. Acute effects of non-narcotic analgesics have been described mainly in association with aspirin and NSAIDs. In high renin states, including salt-depleted normal subjects, NSAID administration may be associated with an acute decrease in renal function, which is more obvious in patients who have underlying renal disease. Clinical syndromes which occur in association with NSAIDs include oedema, hyperkalaemia and acute renal failure and the acute nephrotic syndrome. Acute renal failure may be associated with acute interstitial nephritis and the nephrotic syndrome or may be due to acute tubular necrosis. Patients who have the nephrotic syndrome show fusion of foot processes of glomerular epithelial cells on electron microscopy as well as acute interstitial nephritis. Patients who suffer these episodes of acute renal function deterioration associated with NSAIDs recover slowly after withdrawal of the drugs, and the recovery may not be complete.