The mental and motor development of 24 children with vertically transmitted human immunodeficiency virus (HIV) infection in the first 30 months of life was compared to 27 HIV exposed but uninfected children at the Boston City Hospital and Boston University Medical Center, MA. Bayley Scales of Infant Development, assessed at 4-16 months and at 17-30 months of age, showed that motor development in the infected group was delayed compared to the uninfected seroreverter group in both age periods. Mental development was similar in the two groups at 4-17 months, but was delayed in the HIV infected children at 17-30 months of age. 
COMMENT. Neurodevelopmental outcome in children with HIV infection is variable, but early delay in motor development and late infantile deceleration in mental development can be expected in HIV infected children.