Twelve asymptomatic HIV seropositive subjects ages 21 to 40 years were examined for serologic evidence of cerebral HIV infection, for cerebral structural abnormalities, and for neuropsychologic evidence of cerebral dysfunction using standard methods. Eleven of the 12 had antibody to HIV in the cerebrospinal fluid (CSF). Nine subjects had oligoclonal immunoglobulins in the CSF, of whom five had some for which there were no corresponding serum oligoclonal immunoglobulins ('unique' oligoclonal immunoglobulins). Intracerebral synthesis of HIV specific antibodies was demonstrated for four subjects. Significant deficits of memory and frontal lobe function were found in five of the 12 subjects. Subjects who had oligoclonal immunoglobulins unique to the CSF all had significant neuropsychological abnormalities. No structural cerebral abnormalities were demonstrated using CT scanning for any subject tested. These results support other evidence that HIV is neurotropic and capable of directly inducing brain damage even in immunologically normal subjects. Tests of memory and frontal lobe function are frequently abnormal in patients with early HIV infection, and identify as abnormal a similar group of patients to immunological or biochemical tests which might indicate cerebral HIV infection.