Placental steroid sulfatase deficiency is a genetic disorder only recently reported in the medical literature. Most documented cases of placental sulfatase deficiency have been marked by delay in onset of labor, lack of cervical dilatation, and relative refractoriness of oxytocic agents and amniotomy. We have studied the placenta, cultured fibroblasts, and amniotic fluid cells from an affected patient. The activities of estrone sulfatase, pregnenolone sulfatase, dehydroepiandrosterone sulfatase, and arylsulfatase C in the placenta from the patient were severely deficient. Arylsulfatases A and B were present at levels within the normal range for this tissue. Fibroblast dehydroepiandrosterone sulfatase activity was virtually absent in the patient's cells and present at normal levels in individuals with a variety of lysosomal disorders. It would thus appear that the mutation responsible for steroid sulfatase deficiency is genetically and biochemically distinct from those involved in the lysosomal sulfatase deficiency states. The cell culture studies further suggest that the defect is a generalized one which should be detectable in midtrimester of pregnancy and may have phenotypic consequences in later postnatal life.