The objective of this study was to describe the occurrence of HIV dementia and neuropsychological testing abnormalities in a new cohort of HIV-seropositive individuals at high risk for HIV dementia and to compare these results to a cohort before the advent of highly active antiretroviral therapy (HAART). HAART has been associated with improvements in cognitive performance in some HIV-infected patients. However, it is uncertain whether HAART has changed the frequency of specific neurocognitive abnormalities. Baseline data from 272 HIV-seropositive subjects in the Dana cohort recruited from January, 1994, to December, 1995, and 251 HIV-seropositive subjects in the Northeastern AIDS Dementia Consortium (NEAD) cohort recruited from April, 1998, to August, 1999, were compared. Participants in both cohorts received nearly identical assessments. After adjusting for differences in age, education, gender, race, and CD4 count between the two cohorts, there were no differences in the occurrence of HIV dementia or abnormalities either 1 SD or 2 SDs below established norms for any of the neuropsychological tests. Even though HAART has reduced the incidence of HIV dementia, HIV-associated cognitive impairment continues to be a major clinical problem among individuals with advanced infection.