A simple and safe digestion method has been developed for the simultaneous extraction of arsenic and selenium from fish tissue. A combination of nitric, perchloric and sulphuric acids is used to dissolve, completely, resistant high fat fish tissue at high temperatures without volatilisation losses. Fish samples are digested in test-tubes placed in an aluminium hot-block. Extracts are then analysed automatically by reduction with sodium tetrahydroborate(III) followed by atomic-absorption spectrometry with quartz tube atomisation. The recovery of the method when applied to several organoarsenic and organoselenium species and to National Bureau of Standards Standard Reference Materials was satisfactory.