A rapid semi-automated electrothermal atomisation atomic-absorption spectrophotometric procedure has been developed for the determination of arsenic and selenium in human liver and kidney specimens. The sample is digested with a mixture of nitric and perchloric acids. The nearly dry residue is taken up in hydrochloric acid. The arsenic or selenium in the hydrochloric acid solution is converted into its hydride with sodium tetrahydroborate(III). The hydride is decomposed and atomised in an electrically heated silica furnace, and the atomic-absorption signal is measured at the appropriate resonance wavelengths of arsenic and selenium. Both of the elements can be determined in the biological samples in the range 50–500 ng per gram of wet sample. The method was applied to the determination of arsenic and selenium in about 40 autopsy samples of human kidney (cortex and medulla) and liver taken from Canadian adults living in the Great Lakes Region of Ontario. The arsenic levels in all of the samples analysed were found to be ⩽ 10 ng per gram of wet sample; the median selenium levels in the cortex, medulla and liver were found to be 0.84, 0.31 and 0.39 mg per kilogram of wet sample, respectively.