Early amniocentesis performed at 13 weeks gestation was utilized to obtain amniocytes for culture. Sonicates of cultured amniocytes were used to measure heparin sulfamidase activity for assessment of the status of an at risk pregnancy for Sanfilippo syndrome, type A. The heparin sulfamidase activity was not detectable in cultured amniocytes of the fetus at risk while another enzyme, N-acetylglucosamine 6-sulfatase, was comparable to that of the control. Following termination of the pregnancy, various tissue from the fetus were used for assay of both enzymes. The sulfamidase activity was not detectable in any of the fetal tissue while the 6-sulfatase activity was present in all fetal tissue but varied in activity depending on the type of tissue. Cultured fetal skin and brain contained the highest enzyme activity while skin and liver contained the lowest.