Abstract: A biotechnological process for preparing L(-)-carnitine chloride, having the formula ##STR1## comprising: (a) reacting a racemic ester of (R,S)-3,4-epoxybutyric acid having the formula ##STR2## wherein R is an alkyl group having from 1 to 10 carbons or a benzyl group, with an enzyme capable of selectively hydrolyzing enantiomer S(-);(b) separating the enantiomer S(-) from non-reacted ester which is present in predominantly the R(+) form;(c) reacting the non-reacted ester obtained in step (b) with an enzyme capable of quantitatively hydrolyzing the R(+) form to obtain thereby a salt of 3,4-epoxybutyric acid in the R(+) form having the formula ##STR3## wherein X is Na, K, or Li; (d) reacting the salt obtained in step (c) with a molar excess of trimethylamine; and(e) treating the reaction product of step (d) with HCl to remove excess trimethylamine and to obtain thereby the L(-)-carnitine chloride of formula (I).