It has been reported that non-Caucasian populations often suffer from an atypical type of Parkinson's disease (PD) characterized by poor levodopa response, early cognitive impairment and autonomic dysfunction. We tested the effect of a well known antiparkinsonian compound, amantadine, in 23 Afro-American patients with PD in a time-limited (six months), open-label, clinical and electrophysiological (simultaneously recorded primary and cognitive visual evoked potentials) trial. Patients were given amantadine either as monotherapy (first group) or added to levodopa treatment (second group). Amantadine produced a significant (p < 0.05) shortening of the latency of the event related potential (P300) obtained in a visual discrimination paradigm, while the timing of primary visual evoked potentials was little or not at all affected. Amantadine also showed significant beneficial effects (p < 0.01) on the motor score of both groups as assessed by the Rated Parkinson's Disease Neurological Exam, including items related to autonomic dysfunction. These findings suggest that amantadine alone and as adjuvant to levodopa can significantly improve both the speed of visual cognitive processing and the clinical score in non caucasian patients with PD. For these populations amantadine can be thus considered a helpful therapeutical option.