Methylmercury (MeHg) has been determined in fish reference materials by direct mercury analyzer (DMA 80) and FIA-CV-AAS. In order to evaluate accuracy, certified reference materials (Fish protein, NRCC - Dorm 4 and fish material, Ipen - Dourada 1) were analyzed after extraction and separation of mercury species. Good agreement of the results have been obtained (relative error of the determination between the methods varied from 1.5 % to 39 %). The repeatability of the results varied from 4 % to 26 %.