KOSAKA, K., NAGASAKI, H. and NAKAMURA, R. Finger Tapping Test as a Means to Differentiate Olivo-Ponto-Cerebellar Atrophy among Spinocerebellar Degenerations. Tohoku J. exp. Med., 1982, 136 (2), 129-134-A finger tapping test in which the subject was requested to respond synchronously to the periodic sound signal was performed on 10 patients with OPCA, 10 other SCD and five suspected OPCA. The results indicated that the response of the patients with OPCA was specific among SCD. The response did not more synchronize to the signal above 2.5Hz and a random mixture of two types of the response appeared with frequencies lower and higher than the signal. These delayed and hastened responses represented the characteristic response feature for the patients with SCD except OCPA and those with Parkinson's disease, respectively. Two types of the response were related to cerebellar lesions and to nigrostriatal lesions. The finger tapping test thus offers a useful means to differentiate OPCA among SCD.