The primary objective of this pilot study is to determine the feasibility of giving weekly Laronidase for 2 years in patients with Hurler syndrome after allogeneic transplantation. Specifically, i) the ability to enroll patients, ii) continued compliance throughout the study with drug administration and testing, as well as iii) the relevance of various endpoint determinations will be assessed. The findings of the pilot study will be used to assess whether a subsequent larger study will be conducted.