This study compared 74 human immunodeficiency virus (HIV)-negative and 131 HIV-positive asymptomatic homosexual or bisexual men on an extensive neuropsychological test battery. HIV-positive subjects' performance was significantly worse on verbal memory and psychomotor skills. The prevalence of mild but persistent neurobehavioral impairment in the HIV-positive group was approximately twice that in HIV-negative patients, consistently across several criteria for impairment. There was evidence that degree of neuropsychological impairment was related to patients' perceptions of dysfunction in daily life. Findings were not related to degree of depression or to medication effects. These data suggest that approximately 10% to 20% of HIV-positive asymptomatic men suffer mild neuropsychological impairment that influences their daily lives.