Over 400 patients with lysosomal and peroxisomal storage diseases have received hematopoietic stem cell transplantation from normal donors. Without treatment, all of these diseases have an inexorable fate leading to central nervous system deterioration and early death. On the other hand, all of the engrafted hosts have had a remarkable positive clinical improvement in response to normalization of previously deficient enzymatic activity. Survival data for those engrafted indicates continued life-span as long as two decades beyond transplantation. The particular diseases treated in this way are included in this article. The specific indications and methods for transplantation are also included in this article. Curr Opin Neurol 12: 167-176.