In view of its interesting pharmacological and physiological functions, the enzymic synthesis of the taurine or the beta-aminoethan- alpha-sulfonic acid is described. This compound has been prepared by decarboxylation with rat heart homogenate and at room temperature of cysteic acid obtained by KMnO4 cysteine oxidation. The taurine prepared has been identified by paper and thin-layer chromatography with a taurine pure sample.