There is disclosed a process for the biotechnological resolution, by enzymatic esterification of the corresponding racemic mixture of the S(+) and R(-) optical isomers of the oxazolidinonic compounds having formula (I): ##STR1## wherein R represents a, linear or branched, C.sub.1 -C.sub.8 alkyl group, which process is characterized in that, the racemic 3-alkyl-5-hydroxymethyl-oxazolidin-2-one derivative of formula (I) is reacted with an esterifying compound, selected from esters having formula (III): ##STR2## wherein R represents a, linear or branched, C.sub.1 -C.sub.10 alkyl or alkenyl group and R" represents a linear or branched, C.sub.1 -C.sub.4 alkyl, alkenyl group, a haloalkyl (chlorine, bromine) group or a diacyl glycerolic group or from acids having formula (IV):R'"--COOH (IV)wherein R'" represents a, linear or branched, C.sub.1 -C.sub.20 alkyl or alkenyl group or from anhydrides having formula (V): ##STR3## wherein R.sup.IV represents a, linear or branched, C.sub.1 -C.sub.6 alkyl group, in the presence of an enzyme, immobilized on a porous carrier, capable of giving rise selectively to the esterification reaction of the R(-) isomer, while leaving the S(+) isomer substantially unchanged, which latter is then separated according to known techniques.