Hypomelanosis of Ito (HI) is a neurocutaneous disorder associated with central nervous system abnormalities, including speech delay and intellectual disability. The long term neuropsychological and social characteristics of these children are unknown. Neuropsychological observations and parental reports were obtained yearly on a child with HI from ages 7 to 18 years. Serial measures of intelligence revealed stable verbal and perceptual reasoning scores with later improvements in working memory and processing speed performance. Speech articulation improved at age 12, as did the speed of right-hand finger tapping. Improved social integration occurred, but anxiety persisted throughout this developmental period.