In young adults, a major neurologic complication of HIV-1 infection is cognitive motor impairment. Epidemiologic findings suggest that increasing age is a significant risk factor for HIV-1-associated dementia as the AIDS-defining illness. Findings from the few studies that have directly measured cognition in younger and older HIV-1-infected adults, however, have been mixed, in pan, because of small sample sizes and other methodologic differences between studies. The authors present preliminary findings on cognitive functioning in symptomatic HIV-1-infected younger (aged 20-39 years) and older (aged 50 years or older) adults. Independent of age, HIV-1 infection was accompanied by learning and memory retrieval deficits, which were significantly associated with high plasma viral loads in the young adults. Relative to the younger and older HIV-1-negative (HIV-1-) groups, only the younger HIV-1-positive (HIV-1(+))group had significantly longer reaction times (RTs). Within the older HIV-1(+) group, however, longer simple and choice RTs were significantly correlated with higher viral loads and lower CD4 cell counts. Although HIV-1 infection affects cognition independent of age, longitudinal studies involving large numbers of older individuals are needed to determine whether there are age differences in the prevalence, nature, and severity of HIV-1-associated cognitive dysfunction.