We evaluated and compared procedural memory and auditory P300 event-related potential in age-matched normal controls (n = 15) and drug-naive patients with Parkinson's disease (n = 16). We used Gollin's incomplete picture test for visual procedural memory function and Tower of Hanoi puzzle for visuomotor procedural memory function. The mean latency of P300 was significantly prolonged in the Parkinsonian group than in the controls. In the neuropsychology test, the patients group revealed selective impairment of visuomotor procedural memory against preserved visual procedural memory. In the patients group, the latency of P300 was inversely correlated with performance of visuomotor procedural memory. These results suggest that prolonged auditory P300 event-related potential show the dysfunction of visuomotor procedural memory in the basal ganglia, which appears to be more selectively impaired than visual procedural memory in drug-naive patients with Parkinson's disease.