We report a case of presumed vacuolating megalencephalic leukoencephalopathy (VML) in a 5-year-old boy that was diagnosed when the patient was 34 months old. The patient presented clinically with megalencephaly and delayed onset of slowly progressive neurologic dysfunction. Serial MR imaging and biochemical analysis were performed to differentiate VML from other disease entities with megalencephaly and leukoencephalopathy of infantile onset. Information obtained with diffusion tensor MR imaging revealed nearly intact white matter anisotropy and vectors in parietal and posterior temporal lobes in which hyperintense abnormality was shown on conventional T2-weighted images, and proton MR spectra showed a significant decrease in n-acetylaspartate-creatine + phosphocreatine ratio.