The objective of this study was to characterize the cognitive status of a population of asymptomatic HIV-positive drug addicts (patient group) to document the relationship between neuropsychological results and cerebral blood flow defects as measured by single photon emission computed tomography. As a control group we employed an age-matched population of HIV-seronegative drug addicts. Some neuropsychological differences were found between patients and controls and between drug addicts and normal population. We could not detect any difference in cerebral blood flow rates among HIV-1-positive and -negative drug addicts.