Studies of cognitive function in individuals with HIV infection who remain relatively asymptomatic have shown widely variable estimates of impairment in different races and countries. Limited data exist on the impact of early asymptomatic HIV infection on cognition in developing nations, and indeed none from Nigeria. Hence, this cross-sectional study sets out to determine whether there are differences between Nigerian asymptomatic HIV-seropositive and HIV-seronegative subjects, and whether such differences: if any, could be explained by the degree of immunosuppression (i.e. CD4 cell count). A selected population of 60 heterosexual asymptomatic treatment-naive HIV-positive subjects were administered the Community Screening Instrument for Dementia (CSI-D) to assess language, memory, registration, attention and calculation, recall, praxis and orientation. HIV positives differed from individually matched control subjects in certain measures of language expression, registration, attention and calculation, orientation to time, motor response and total CSI-D scores. The CD4 cell count of the HIV-seropositive subjects had no significant correlation with the cognitive test scores.