Process for the stereoselective reduction of chiral .alpha.- or .beta.-keto esters which have a chiral center in the .gamma. position in an inert solvent at temperatures from -80 to +50.degree. C. using a reductant obtained by reaction of NaBH.sub.4 and (D)- or (L)-tartaric acid, to give the corresponding diastereomeric hydroxy compounds in each case.