We administered a battery of computerized and conventional neuropsychological measures to a group of 507 HIV-1 seronegative, 439 asymptomatic HIV-1 seropositive (Centers for Disease Control [CDC] groups 2 and 3), and 47 symptomatic HIV-1 seropositive (CDC group 4) homosexual/bisexual men enrolled in the Los Angeles center of the Multicenter AIDS Cohort Study. Tasks included multiple measures of attention, reaction time, memory, and psychomotor speed. Comparison of group means revealed significant differences in performance between HIV-1 seronegative and symptomatic HIV-1 seropositive men on computerized measures of choice reaction time and on conventional measures of memory and motor speed. These findings are consistent with previous research in this area and support the sensitivity of both computerized and conventional neuropsychological instruments for detecting cognitive changes found in symptomatic HIV-1-infected individuals. Asymptomatic seropositive men, on the other hand, did not differ significantly from seronegative subjects on any of the computerized or conventional neuropsychological measures. Only 13% of the asymptomatic HIV-1 seropositive men showed abnormal performance on a composite measure of cognitive functioning from the computerized test battery. This proportion did not differ significantly from that of seronegative controls (14%), but was significantly lower than the percentage of abnormal findings observed among symptomatic HIV-1 seropositive subjects (28%). Thus, results from this study support the hypothesis that the frequency of neuropsychological abnormalities in asymptomatic HIV-1-infected homosexual men is low and not statistically different from that of seronegative controls.