Arylsulfatase C [EC 3.1.6.1] was solubilized from rat liver microsomes with Triton X-100 and purified about 2,000-fold with an overall yield of 30-40%. The purification procedure included ion-exchange chromatography, hydrophobic affinity chromatography, and gel filtration. The purified enzyme was homogeneous as judged by polyacrylamide gel electrophoresis in the presence of SDS, and its monomeric molecular weight was estimated to be about 72,000 daltons. The molecular weight of the native enzyme was about 280,000 daltons as determined by gel filtration in the presence of Triton X-100, suggesting a tetrameric structure for the enzyme molecule. The enzyme showed an isoelectric point of pH 8.1. From its strong affinity toward concanavalin A-Sepharose and colorimetric determination of neutral sugars by the phenol-sulfuric acid method, arylsulfatase C was identified as a glycoprotein. Analysis of the carbohydrates by gas-liquid chromatography demonstrated that the carbohydrate chains of arylsulfatase C were rich in mannose and N-acetyl-glucosamine, suggesting that they are the high mannose-type. This conclusion was supported by the results of digestion of the enzyme with endoglycosidase H.