One of the most serious effects of HIV disease in children is neuropsychological deterioration (relating to mental and nervous system functioning). This complication affects the vast majority of HIV infected children. A previous study of continuous intravenous administration of AZT in pediatric patients with HIV infection showed consistent and dramatic improvements of symptoms in all patients that had shown neurodevelopmental deficits or abnormalities. These improvements were seen within 3 to 4 weeks after AZT treatment was started. Neurodevelopmental improvements have been sustained on AZT, usually showing steady improvement which, in some patients, was associated with restoration of pre-HIV intellectual and neurological function. This study also showed an increase in the IQ scores of children receiving continuous infusion of AZT who did not have overt clinical evidence of encephalopathy (disease of the brain). Thus changes in cognitive function may be among the earliest signs of AIDS encephalopathy and underscores the need to start therapies that will treat the central nervous system in patients who appear to be clinically intact. A study comparing continuous infusion to intermittent dosing of AZT showed a significant increase in IQ scores for those children receiving the continuous dose compared to those treated with the intermittent schedule. Although a portable infusion pump allows patients to receive continuous infusion of AZT, a sustained release oral formulation that could provide a continuous release of AZT into the bloodstream would be highly desirable.