Nocardia tartaricans converted sodium cis-epoxysuccinate to L-tartrate. The highest cis-epoxysuccinate hydrolase activity (37.7 U mg(-1)) was obtained with 0.02% (w/v) sodium deoxycholate, but this inactivated the cells. Immobilized N. tartaricans in pectate gel showed higher enzyme activity (51 U mg(-1)) compare to the free cells (8.9 U mg(-1)). After 450 days, the immobilized cells still possessed 0.65 U mg(-1), i.e. 30% of the initial enzyme activity.