Homogeneous arylsulfatase A from human placenta, liver and urine contains two nonidentical subunits of 59 and 54 kDa. The two subunits are immunologically identical. The relative amount of low molecular weight subunits is only 20-30% of the total enzyme protein. Treatment of the enzyme under various conditions with endo-beta-N-acetylglucosaminidase F results in a decrease in the apparent molecular weight of both subunits by 1-2 kDa. a value that corresponds to the loss of a single N-linked oligosaccharide. However, as judged by carbohydrate staining, endo-beta-N-acetylglucosaminidase F does not remove all carbohydrate from the subunits or from glycopeptides of arylsulfatase A. In contrast, human prostatic acid phosphatase, a glycoprotein with a high content of mannose, hybrid and complex oligosaccharides is completely deglycosylated under identical experimental conditions. Several attempts to deglycosylate arylsulfatase A by chemical methods were unsuccessful due to poor recovery of the protein. From the present studies we conclude that arylsulfatase A contains an endo-beta-N-acetylglucosaminidase F resistant, perhaps O-linked carbohydrate.