Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of often chemically unrelated compounds with some common therapeutic actions and side effects. They have potent anti-inflammatory, analgesic and antipyretic activity, and are among the most widely used drugs worldwide. It is generally thought that one of their main mechanisms of action is the inhibition of cyclo-oxygenase (COX), the enzyme responsible for biosynthesing the prostaglandins and thromboxane. NSAIDs are also associated with an increased risk of adverse gastrointestinal, renal and cardiovascular effects. This review describes the clinical pharmacology of NSAIDs, their classification, molecular mechanisms of action and adverse effects, including their possible contribution to neuro-inflammation and carcinogenesis, as well as some recent developments aimed at designing effective anti-inflammatory agents with improved safety and tolerability profiles.