Renal reserve is believed to be diagnostic dynamic method for accessing both early renal failure and renal vascular reactivity. The aim of our study was to follow renal reserve during 12 month therapy with omega-3 polyunsaturated fatty acids. Omega-3 was given orally of a: 540 mg of eicosapentaenic acid and 810 mg of docosaheksenic acid daily. Before and after 12 month of therapy renal reserve (expressed as % change of basal creatinine clearance) was estimated during i.v. dopamine infusion in dose 2 ug/min/b.w. Twelve month therapy was associated with increase of renal reserve (respectively 14.86 +/- 16.35 vs 30.25 +/- 14.27%), HDL cholesterol (respectively 47.55 +/- 11.49 vs 58.05 +/- 7.89 mg/dl) and decrease 24 hrs proteinuria (respectively 3.31 +/- 2.01 vs 1.31 +/- 1.37 g/24 h), total cholesterol TCH (respectively 251.15 +/- 50.91 vs 214.15 +/- 24.09 mg/dl), LDL cholesterol (respectively 170.0 +/- 47.22 vs 124.15 +/- 17.93 mg/dl), serum uric acid (respectively 7.53 +/- 1.01 vs 5.59 +/- 0.88 mg/dl), fasting insulinemia (respectively 11.27 +/- 5.28 vs 9.20 +/- 4.80 U/ml) for p < 0.05. The statistically significant correlation coefficient were found only between following parameters: % renal reserve vs insulin (r = -0.55, p < 0.05), delta 24 h proteinuria vs delta TCH (r = 0.69, p < 0.05), delta 24 h proteinuria vs delta LDL (r = 0.51, p < 0.05). Our study suggest that omega-3 therapy improves renal reserve and its effect is to some extend related to improvement of some metabolic disturbances. Also this therapy ameliorate proteinuria which is linked with lipid lowering effect of omega-3.