Rhodanese and 3-mercaptopyruvate sulphurtransferase have been identified in A. vinelandii. Two distinct active fractions of the two sulphur transferases were obtained after FPLC ion-exchange chromatography of material partially purified from crude extracts. Rhodanese has been purified to homogeneity, and it consists of one polypeptide chain of Mr ca 25,000. A partial purification of 3-mercaptopyruvate sulphurtransferase was obtained.