The hydrolysis of L-leucyl-γ-substituted D,L-glutamates by leucine aminopeptidase, from porcine kidney, is stereospecific with erythro-γ-methyl and erytho-γ-fluoroglutamate containing dipeptides whereas there is a lack of stereospecificity with the erytho-isomers. The optical purities of L-threo- and L-erythro-glutamate isomers thus obtained have been monitored by gas chromatography, high pressure liquid chromatography, or nuclear magnetic resonance. The optical rotations of optically pure L-isomers have been measured and the discrepancies with former publications are discussed.