We describe a case of severe aortic stenosis in a 16-year-old male with Hurler's syndrome who had prior bone marrow transplantation. The excised aortic valve leaflets showed characteristic pathologic findings of Hurler's syndrome. This is the first case report of aortic valve replacement in a patient with Hurler's syndrome treated with bone marrow transplantation that demonstrates progression of the aortic valve disease despite treatment.