Enzyme replacement therapy (ERT) has been developed for mucopolysaccharidosis I (MPS I), a lysosomal storage disorder. ERT helps many physical ailments due to the disease, but does not treat the central nervous system, due to inability to cross the blood brain barrier. Our purpose is to test delivery of ERT to the spinal fluid via intrathecal injection in patients with MPS I. In this pilot study, we will use recombinant human α-L-iduronidase administered intrathecally once per month for four months to individuals with the Hurler-Scheie and Scheie forms of MPS I and spinal cord compression. If successful, intrathecal delivery could represent a practical, straightforward method of treating central nervous system disease due to lysosomal storage.