Most of studies on omega-3 fatty acids (omega-3) supplementation in patients with rheumatoid arthritis (RA) have clearly shown potentially beneficial changes in cytokine and eicosanoid metabolism. The overall clinical improvement, however, has been only moderate. One explanation is that an increased intake of omega-3 leads to a reduction in the availability of antioxidants and an increased generation of lipid peroxides. The majority of the anti-inflammatory drugs routinely used nowadays are COX (cyclo-oxygenase) inhibitors. Mechanism of COX II inhibitors is similar of omega-3. So, it is difficult to differentiate omega-3 net effects in some situations. Existing clinical trials on omega-3 and vitamin E (Vit E) are sometimes questioned due to using omega-6 fatty acids as placebo and neglecting omega-6 fatty acid intake in the diet. A comprehensive randomized controlled double-blind trial would have omega-6 fatty acids served as placebo in patients who are well matched in terms of therapies and drugs.