Atomic absorption spectrometry with electrothermal atomization still remains one of the important techniques for elemental analysis of clinical materials. The correct sampling procedure, sample handling, stabilization and storage are integral components of the analysis. The paper summarizes recent knowledge concerning, above all, harmonization of the procedures of sampling, sample preparation, and analysis of blood and urine and the inspection of result quality. The conditions of analysis of the most frequently determined elements in the above matrixes and the rules for sampling of hairs and their preparation for analysis are discussed.