Eight of 13 children pre- or perinatally infected with the HIV virus subsequently developed neurological symptoms. Three children also had other nonspecific symptoms (fever, lymphadenopathy, diarrhoea, hepatosplenomegaly, failure to thrive and mucocutaneous thrush). Five children developed illnesses associated with AIDS (opportunistic infections, cachexia and lymphocytic interstitial pneumonia). The neurological abnormalities predominantly affected motor functions, only later also involving sensory ones. Motor, cognitive and language development was impaired in all eight children. A loss of developmental milestones occurred in three children with HIV encephalopathy: they have since died. In all the children the HIV infection caused symptoms within the first year, progressing more quickly in the three with encephalopathy. There were no discernible risk factors to account for the difference in the course of the disease.