We present the direct and stereoretentive deuteration of primary amines using Ru-bMepi (bMepi = 1,3-(6'-methy1-2'-pyridylimino) isoindolate) complexes and D2O. High deuterium incorporation occurs at the alpha-carbon (70-99%). For a-chiral amines, complete retention of stereochemistry is achieved when using an electron-deficient Ru catalyst. The retention of enantiomeric purity is attributed to a high binding affinity of an imine intermediate with ruthenium, as well as to a fast H/D exchange relative to ligand dissociation.