The aim of the study was to adapt the method of selenocysteine content determination elaborated by Jones et al. and Cone et al. for some oxidoreductive enzyme analysis. Determination was based on usage of conventional amino acid analyzer. Modification consisted in introducing the stage of yeast protein purification from reagents after carboxymethylation process containing selenocysteine with iodoacetic acid according to procedure described by Tappel et al., as well as applying the internal standard during analytical procedure. Application of amino acid analyzer made it possible to separate selenocysteine from other components of the sample analyzed which was sufficient for quantitative measurement. Internal standard used eliminated errors resulting from additional preparation: the necessity for amino acid coupling with iodoacetic acid, purification of complex from the excess of reaction agents as well as inaccuracy commonly made during solution pipetting and dosing onto the chromatographic column.