Enzymatic hydrolysis of synthetic methyl 5-, 9-, and 12-thiastearates in aqueous media withCandida cyclindracea or porcine pancreatic lipases gave the corresponding fatty acids in 70–100% yield. Hydrolysis of the 3- and 4-positional isomers gave only 15–25% of the free thia fatty acids, suggesting discrimination against these isomers by lipases. No lipolysis was achieved with methyl 2-thialaurate under a range of reaction conditions. Esterification of the 3-, 4-, 5-, 9-, and 12-thiastearic acids withn-butanol inn-hexane using Lipozyme (immobilizedRhizomucor miehei) as the biocatalyst gave the corresponding butyl esters in 80–95% yield. Interesterification (acyl exchange) of triolein with methyl 9-thiastearate in the presence of Lipozyme showed the incorporation of 9-thiastearoyl chain at only one of the α-positions of triolein. In the case of methyl 2-thialaurate, no lipase-catalyzed acyl exchange reaction was possible. This study showed that the position of the sulfur atom in thia fatty esters affects the lipase-catalyzed hydrolysis and interesterification reactions.