A simple and rapid procedure for the simultaneous determination of methylmercury and Hg2+ in fish reference materials was developed. The procedure was based on a rapid (2.5 min) microwave-assisted solubilization of biomaterial with tetramethylammonium hydroxide, simultaneous quantitative ethylation-extraction of the mercury species into hexane (15 min) and flash isothermal separation (15-30 s) using a multicapillary regular column (100 cm) or a minicolumn (22 cm). The chromatographic hardware necessary for sample introduction into a microwave induced plasma was downscaled to a split injection port and a 20 × 20 × 10 cm compartment (housing the 1 m column) or a 22 cm × 1 cm od thermally insulated tube (housing the minicolumn) maintained at a constant temperature and connected directly to the detector. No dilution of the GC eluent (60-120 ml min-1) with make-up gas was necessary to achieve optimum sensitivity. Detection limits (as Hg) were 0.5 pg ?l-1 (20 ng g-1 dry mass) and 2 pg ?l-1 (80 ng g-1 dry mass)for MeHg+ and Hg2+, respectively. The method was validated for speciation analysis for mercury in BCR 463, BCR 464 (Tuna Fish) and NRCC DORM-1 (Dogfish Mussel) certified reference materials.