Non-steroidal anti-inflammatory drugs (NSAIDs) are often prescribed to patients with rheumatoid arthritis (RA), as the first line drugs, and are administered over a long term. NSAIDs are classified principally into acidic and basic preparations, and the former is more widely used for the treatment, since the latter possesses no anti-rheumatic effect. Moreover, the acidic NSAIDs are classified into salicylates, arylacetic acid, pyrazolone, fenamates and oxicams. Arylacetic acid has a strong analgesic effect. Pyrazolone is well balanced between analgesic, anti-inflammatory and antifebrile effects. The fenamates and oxicams are long acting. On the other hand, NSAIDs sometimes inhibit adverse reactions, such as gastroduodenal diseases and renal insufficiency, which are probably induced by the inhibition of cyclo-oxygenase to reduce prostaglandin content. Therefore, appropriate NSAIDs must be selected after consideration on the character, property and adverse reaction of each drug.