After almost 90 years of clinical use, aspirin remains one of the world's most extensively used 'over-the-counter' drugs, and it is still recognised as the standard analgesic/antipyretic/anti-inflammatory agent by which newer drugs are assessed. However, its pre-eminent position as the analgesic of choice for mild to moderate pain has been seriously challenged with the introduction of many 'new' non-steroidal non-narcotic analgesic drugs. Indeed, there is convincing scientific evidence that many of the 'newer' non-steroidal drugs such as diflunisal, ibuprofen, flurbiprofen etc. are significantly superior analgesics and, in many cases, have a longer duration of action. In recent years the salicylates, aspirin in particular, have been the focus of much attention regarding their side effect profiles. At usual dosages for relief of pain and during occasional use, aspirin is well tolerated by the vast majority of patients. Adverse reactions, of which there is a wide spectrum, most frequently accompany anti-inflammatory doses of aspirin, or may be the result of accidental overdosing (particularly in children and the elderly)--probably a reflection of the lay population's acceptability of aspirin's presumed safety. As with other non-steroidal analgesic drugs, gastrointestinal complaints are the most commonly reported side effects. The existence of many shared clinical, adverse and toxic effects of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) is thought to be accounted for by a common mechanism--inhibition of the ubiquitous cyclo-oxygenase enzyme. Thus, suppression of prostaglandin biosynthesis is widely considered to explain the common properties of NSAIDS, although further research is still necessary to clarify some inconsistencies and to complete our understanding of the processes involved. Aspirin and salicylates have been reported to have a wide range of drug interactions but only relatively few seem to be clinically important. Many of the interactions are pharmacokinetic in nature. Drugs considered to produce the most significant interactions with salicylates include anticoagulants and thrombolytic agents, uricosuric agents, corticosteroids, methotrexate and sulphonylurea hypoglycaemic agents.