AIMS: Nutrition as an aetiological factor participates a great deal in premature atherosclerosis in haemodialysis (HD) patients. The basic mechanisms of end-stage renal disease and premature atherosclerosis are connected with changes in cell functions at the membrane level. We investigated the red cell membrane fatty acids and the effects of fish oil supplements on nutritional status and inflammatory markers in HD patients. METHODS: We examined 42 HD patients (mean age 55 +/- 8 years). The control group consisted of 16 healthy subjects of similar age and sex to the tested group. HD patients were administered supplements with 2.4 g of n-3 polyunsaturated fatty acids per day for 2 months. Before and after supplementation, we examined plasma lipids, cell membrane erythrocyte phospholipids content, serum albumin, haemoglobin, interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha). RESULTS: Baseline values in the tested group confirmed the presence of essential fatty acids deficiency. A statistically significant negative correlation between TNF-alpha and eicosapentaenoic acid (EPA) (r = -0.497; P < 0.05) and IL-6 and EPA (r = -468; P = 0.03) was found in HD patients before supplementation. There was a significant increase in docosahexaenoic acids, high density lipoprotein cholesterol, plasma albumin, haemoglobin levels in HD patients after supplementation (P = 0.0001). There was a significant increase in EPA (P = 0.01) after treatment, and there was a significant decrease in inflammatory markers (IL-6 and TNF-alpha, P = 0.0001) after supplementation in the tested group. CONCLUSION: A dietary regime with fish oil could be used in dialysis patients to slow down the development of atherosclerosis and improve nutritional parameters.