A patient with enzymatically proven Sanfilippo disease type B is presented. This type of mucopolysaccharidosis results from deficient o-N-acetylglucosaminidase activity leading to defective degradation of heparan sulphate. As this disease is associated with high morbidity and mortality, different therapeutic approaches are under investigation. Bone marrow transplantation is among these new choices of management. The value of bone marrow transplantation in the mucopolysaccharidoses, especially in MPS IIIB, is discussed with a wide review of the literature.