A comprehensive study of the critical taxon Leymus buriaticus Peschkova was carried out in comparison with natural and cultivated populations of L. littoralis and L. chinensis from various localities in Buryatia. The factorial analysis performed by 15 morphological characters showed that L. buriaticus occupied an intermediate position between L. chinensis and L. littoralis. SDS-electrophoresis of individual seeds showed presence of similarity of relations between samples identified as L. buriaticus and selected samples of L. littoralis and L. chinensis in mixed population from a classical locality. The analysis of subfractional composition of histon Н1 also revealed presence of common subfractions of L. littoralis, L. chinensis and L. buriaticus. It was concluded that the endemic L. buriaticus was of a hybrid origin.Key words: Leymus, L. buriaticus, L. littoralis, L. chinensis, taxon, morphotype, systematization, SDS-electrophoresis, grain storage proteins.