A Study Investigating the Relationship Between the Development of Laronidase Antibody and Urinary GAG (Glycosaminoglycan) Levels in Aldurazyme® Treated Patients

Inclusion Criteria: * Have a documented diagnosis of MPS I confirmed by measurable signs and symptoms and deficient α-L-iduronidase activity (\<10% of the lower limit of normal). * For a patients receiving Aldurazyme therapy prior to study entry: Have available as baseline data the results of urinary GAG levels and IgG antibody titers collected prior to the patient's first Aldurazyme infusion. * Provide signed, written informed consent prior to any protocol-related procedures being performed. Consent of a legally authorized guardian(s) is (are) required for patients under 18 years. Exclusion Criteria: * Have previously received Aldurazyme without the collection of baseline samples as specified. * Have a suspected hypersensitivity to Aldurazyme or a know hypersensitivity to components of infusion solution. * Have received a Hematopoietic Stem Cell Transplantation, injection fibroblast therapy, or major organ transplant. * Are receiving chronic immunosuppressant therapy. * Have a medical condition, serious intercurrent illness, or other extenuating circumstances that may interfere with study compliance including all prescribed evaluations and follow-up activities. * Are pregnant or lactating * Have received investigational drug within 30 days prior to study enrollment