Haloacetate halidohydrolase II specified by a plasmid pUO1 was purified from haloacetateassimilating Moraxella sp. B. The purification procedures included protamine treatment, Ammonium sulfate fractionation, and column chromatographies with DEAE-cellulose, hydroxyapatite and Bio-gel P-150, resulting in a 200-fold purification. The purified enzyme was homogeneous by criteria of ultracentrifugation and disc electrophoresis. The molecular weight estimated by Sephadex G-100 gel filtration was 43, 000, and it was 26, 000 by SDS-polyacrylamide gel electrophoresis. The sedimentation coefficient s020, w was 4.1 S, and the isoelectric point was pH5.2. The amino acid composition was also estimated. The enzyme catalyzed the dehalogenation of monochloro-, monobromo-and monoiodoacetate, but not monofluoroacetate. 2, 2-Dichloroacetate and 2-chloropropionate were slightly dehalogenated, but trichloroacetate and 3-chloropropionate were not. The enzymewas very sensitive to inhibition with thiol reagents.