Multiple electrophoretic species of arylsulfatase were demonstrated in sonicates of Proteus rettgeri by paper electrophoresis. Subsequent treatment of the sonicates with streptomycin sulfate and DEAE-cellulose chromatography resolved enzyme activity into four fractions. Electrophoretic examination of each chromatographic fraction revealed sulfatase heterogeneity comparable to that of the initial extract. These electrophoretic components differed in their general response to a number of arylsulfatase inhibitors. The results are discussed in relation to the finding of multiple species of arylsulfatase in other biological systems.