Motor (postural tremor of the outstretched hands, most rapid voluntary alternating index finger movements and rise times of most rapid voluntary isometric index finger extensions) and psychometric tests (multiple choice vocabulary test - form b, syndrome short test, the German version of the standard progressive matrices - Raven, and the psychic and somatic findings according to the AMDP-system) as well as MRI-Scans were analysed in 100 HIV-infected patients of all stages according to the actual CDC-classification, but without any central-nervous or psychic deficit. Patients with drug, alcohol or tranquilizer abuse, opportunistic, cerebral infections or fever were excluded from the study. Tremor-peak-frequencies and reaction times did not show any significant difference to an age- and sex-matched control group; the other motor parameters revealed significant slowing in the patient group and a worsening with the CDC-stages. MRI-scans of all the patients were normal. The psychometric tests did not show significant alterations on a group statistical level, especially not in the depression scales. Morphologically, the motor performances of the HIV-infected patients resembled those of patients with basal ganglia diseases (M. Huntington, M. Wilson, M. Parkinson). Correspondingly, in some cases of clinically demented HIV-positive patients, MRI-scans showed lesions in the basal ganglia. It can be concluded, that there is an early subclinical central-nervous system affection in HIV-infected patients, especially of the basal ganglia, detectable with appropriate motor function tests sometimes considerably preceeding structural deficits seen later in the course of the disease in MRI-scans.