Two different tribes of Mordvinians, Erzia and Moksha, were studied with respect to 13 different genetic marker systems. The Erzia and Moksha were shown to be fairly homogeneous; a significant gene frequency difference was found only in the MN blood group system. Estimation of the genetic distances revealed that Mordvinians showed the closest relationship to the Maris and to populations of the western Finno-Ugrian linguistic group such as Finns, Estonians and Karelians.