Importance: We sought to illustrate improvement of cerebral white matter changes in metachromatic leukodystrophy after treatment with hematopoietic stem cell transplant (HSCT). Observations : We conducted serial magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (1H-MRS) as standard follow-up after HSCT with cord blood in 1 patient with juvenile metachromatic leukodystrophy diagnosed before frank degenerative symptoms developed.Wemeasured MRI and 1H-MRS changes. The white matter changes first increased after HSCT, then decreased in relation to the pre-HSCT MRI and 1H-MRS. Conclusions and Relevance: Hematopoietic stem cell transplant, if performed early in metachromatic leukodystrophy, can not only stabilize but even improve cerebral white matter abnormalities. Our findings suggest a biological effect of HSCT. ©2013 American Medical Association. All rights reserved.