To evaluate cognitive impairment in the early stages of HIV infection in intravenous drug users (IVDUs) we have studied 39 consecutive HIV-infected subjects (CDC stage II-III) whose only known risk factor for the infection was intravenous heroin addiction. The control group was represented by 30 seronegative IVDUs. All subjects were tested with an extensive neuropsychological battery assessing general intellectual abilities and single cognitive functions. The patients differed from controls only for tests of attention and visual-motor abilities: 20% of asymptomatic seronegative and PGL patients showed alterations in two or more cognitive tests, as opposed to 3% of controls (p < 0.001). Our findings suggest that cognitive deficits seem to be present in a substantial percentage of IVDUs with asymptomatic HIV infection. Cognitive damage at this stage seems to selectively involve attention and visual-motor abilities, sparing general intellectual performances.