End stage renal disease (ESRD) is a condition that inflammation plays an important role in damaging to tissues, especially in vascular system. The effect of omega-3 fatty acids is well documented in some inflammatory diseases via eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) components of fish oil. The aim of this study was to investigate the effects of dietary omega-3 fatty acid supplementation on levels of inflammatory parameters in ESRD patients. In this study, 40 patients with 18 years old, at least, arrived if they are on chronic ambulatory peritoneal dialysis for 3 months. If patient have chronic diarrhea, malignancy, thrombocytopenia(less than 100000/mm3, coagulation disorders, need to anticoagulant drugs exclude from study. Group 1 (20 patients) using omega 3 capsules, 1000mg, manufactured by Zahravi Pharmaceutical, 3 times a day for 2 months. Group 2 (20 patients) using placebo capsules, manufactured by Zahravi pharmaceutical, 3 times a day for 2 months. Serum level of Interlukin-6 and C-reactive protein(CRP) are measured at beginning and end of the study.