We have been studying the chiral lanthanide NMR shift reagents (CLSR) which can be used for determination of the absolute configurations of organic compounds. We first reported that Eu(III)-pdta complex can be used for α-amino acids in 1987. However, as the other lanthanide shift reagents, this reagent caused serious line broadening especially when we used the reagents on a high-field apparatus. We solved this problem by use of Sm(III) as a central metal ion. This reagent, Sm-pdta, enables to detect the enantiomer signal separations not only of α-proton signals but also of the side-chain proton signals. The reagent affordded a consistent correlation between the absolute configuration and the relative positions of enantiomeric signals of both α-protons and side chain protons as shown in Scheme 1. The major drawback of this reagent is that the signals due to pdta ligand of this reagent often overlapped with proton signals of substrates. We improved the reagent by replacing the hydrogens of the methylene part of the acetate groups with deuteriums. This removal of the obstructive signals allowed a measurement for a dilute solution of substrate (〜1mM). Moreover, it also allowed the simultaneous determination of absolute configurations of 2〜10 α-amino acids in mixture. Absolute configuration of each amino acid in a mixture was correctly assigned on the basis of the relationship which was observed for single amino acids. We believe that this NMR method must be practical for determining absolute configurations of peptides from natural sources.