This meta-analysis summarizes the broad spectrum of neuropsychological research on HIV disease across a sample of 41 primary studies and an aggregate of 8,616 participants for 10 major neuropsychological ability areas. Analyses of the course of cognitive decline within and across Centers for Disease Control classifications reveals statistically significant cognitive deficits from asymptomatic HIV to AIDS. Effect sizes (Cohen, 1988) were calculated to reflect between-group (asymptomatic, symptomatic, AIDS) differences in each neuropsychological domain. Relatively small effect sizes were obtained for the asymptomatic (0.05–0.21) patients, and generally small to moderate effect sizes were obtained for symptomatic (0.18–0.65) HIV+ patients, with motor functioning exhibiting the greatest effects in this later disease stage. The most notable deficits in cognitive functioning were found in the AIDS group with moderate (attention and concentration) to large (motor functioning) effect sizes with values ranging from 0.42–0.82. Comparison of cognitive functioning as a function of disease progression revealed that motor functioning, executive skills, and information processing speed were among the cognitive domains showing the greatest decline from early to later stages of HIV. These findings indicate that cognitive deficits in the early stages of HIV are small and increase in the later phases of the illness, and that specific patterns of cognitive deficits can be detected with disease progression. These results and their clinical utility are further discussed. (JINS, 2002, 8, 410–424.)