Adult-onset metachromatic leukodystrophy (MLD) is very rare with a combination of cognitive and behavioral symptoms and peripheral polyneuropathy. A 47-year-old man was admitted due to memory impairment, gait disturbance, dysarthria and personality changes for a period of 3 years. The arylsulfatase A level in his leukocytes was decreased. A brain MRI showed bilateral symmetrical demyelination but nerve conduction velocities (NCV) were normal. We report a very rare case of adult-onset MLD with normal NCV.