An alternative method to acid digestion is presented for the preparation of marine biological tissues and botanical samples for trace metal determination by ETAAS. Samples were solubilized using a methanolic solution of tetramethylammonium hydroxide (TMAH), either overnight at room temperature or by the application of heat and/or ultrasonic agitiation. Following dilution with water, aliquots were sampled into a graphite furnace using a conventional autosampler. External calibration was used for all analyte determinations. Limits of detection, characteristic mass and precision are reported for copper, cadmium, nickel, lead, manganese and chromium. Measured concentrations are in satisfactory agreement with certified values for the biological reference materials DORM-2, DOLT-2, TORT-2 and BCR 060. Samples prepared with TMAH can be stored for up to 3 years at room temperature without any change in analyte concentrations. Experimental InstrumentationA Perkin-Elmer (Norwalk, CT, USA) Model 5000 atomic absorption spectrometer fitted with continuous source background correction and equipped with an HGA 500 furnace and AS 60 autosampler was used for Cu, Cd, Pb, Ni and Mn