A method has been developed for the assay of arylsulfatase C in tissue extracts containing arylsulfatases A and B. Significant variation of enzyme activity was observed among 26 inbred murine strains. Activity differences were apparent at all stages evaluated between 1 and 70 days postnatal age. Arylsulfatase C from representative high- and low-activity strains exhibited similar Michaelis constants, temperature optima, pH optima, thermostabilities and inhibitor profiles.