The proposed study would assess different components of attentional functioning in children with HIV-1 disease. A quantitative and systematic method is developed that could complement the existing standardized instruments used for measuring attention and neurocognitive function in this population. Simple alerted visual reaction time will be measured with varying preparatory intervals, a two-choice reaction time in a go/no-go paradigm will be administered, and a continuous performance, divided reaction time test and an object decision task will be given. Performance on these measures will also be related to measures of brain structure and stage of HIV-1 disease.