Abstract: The aim of this study was showing the suppressive effect of fish oil supplementation on clinical symptom in rheumatoid arthritis. Forty two patients with Rheumatoid Arthritis (RA) entered a trial to determine the clinical and biochemical effects of dietary supplementation with fractionated fish oil fatty acids. A randomized study design with 4 and 8 week treatment periods were used. Treatment with non-steroidal anti-inflammatory drugs and with disease modifying drugs was continued throughout the study. There were significant improvement of RF (p = 0.009), ESR (p = 0.003) and serum CRP (p = 0.002) after 8 weeks fish oil supplement, but after 4 weeks the RF (p = 0.004) only showed significant improvement. This study shows that dietary fish oil supplementation is effective in suppressing clinical symptoms of rheumatoid arthritis.