Language deficits are a major characteristic of neurobehavioral dysfunction in pediatric HIV disease. An object decision task, which assessed reaction time facilitation following a semantic or identical prime in comparison to an unrelated prime, was used to investigate whether semantic processing abnormalities could be responsible, in part, for these deficits. Thirty children with vertically acquired HIV infection (M age 9.0 years; range 6–13) participated. Either a picture of the same object (repetition prime), a semantically related object (semantic prime), a semantically unrelated object, or a nonsense object preceded a target picture, which in 50% of the cases was a real object. Brain scans of children were rated and used together with neurobehavioral functioning to classify children as having HIV-related CNS abnormalities (n = 13) or not (n = 17). Increased semantic priming but not repetition priming was associated with a greater degree of cortical atrophy. Furthermore, CNS compromised children had significantly faster reaction times following a semantic prime compared to an unrelated prime than non-compromised patients. This facilitation following semantic priming for the CNS compromised patients (13.3%) almost equaled the facilitation following repetition priming (15.3%) while for the non-compromised patients facilitation following semantic priming (7.9%) was clearly smaller than following repetition priming (14.6%). These data suggest that HIV infection in children may result in a reduced neural network leading to impoverished semantic representations characterized by poor differentiation between closely related objects. (JINS, 2001, 7, 491–501.)