Three groups of female rats(n=6 per group) were exposed to 1 and 10 mg/L of sodium arsenate for 90 days. The antioxidant and peroxidation parameters in kidney and liver tissues were evaluated, also the fatty acid composition were determined. In liver the synthesis pathway of n-3 polyunsaturated fatty acids(PUFA) seemed to be more affected than the n-6 PUFA, while in kidney the n-6 pathway was more affected. The Δ5 ‘desaturase index’ was decreased in kidney. Both in liver and kidney an increase in the percentage of trans PUFA was observed, also we noted a disturbance in antioxidant parameters as SOD, GPx, CAT, and GSH(P<0.05). While the protein carbonyl levels increased only in liver. Three groups of female rats (n = 6 per group) were exposed to 1 and 10 mg / L of sodium arsenate for 90 days. The antioxidant and peroxidation parameters in kidney and liver tissues were evaluated as also the fatty acid composition were determined. In liver the synthesis pathway of n-3 polyunsaturated fatty acids (PUFA) seemed to be more affected than the n-6 PUFA, while in kidney the n-6 pathway was more affected. in liver and kidney an increase in the percentage of trans PUFA was observed, also we noted a disturbance in antioxidant parameters as SOD, GPx, CAT, and GSH (P <0.05). While the protein carbonyl levels increased only in liver.