The determination of Se in serum by atomic absorption spectrometry with electrothermal atomization is presented. The method has the detection limit of 12.9 pg Se, which was determined with 100 ml samples. The method was verified using the standard reference material - Seronorm^TM Trace Element Serum, NYCOMED PHARMA AS, Norway. The median level of Se in the serum of healthy volunteers from Bratislava (Slovakia) was 83.6 mg.l^-1). The median concentrations of Se in the serum of male donors were higher (85.7 mg.l^-1) than in female donors of the similar age (80.1 mg.l^-1).