A clinical evaluation of 10 patients with Machado-Joseph disease (MJD) was performed by using an acoustic analysis soft (SoundScope, GW Instruments Inc) before and on 4 weeks of treatment of taltirelin hydrate (TH). A rapid repetitive monosyllable/ka/was recorded as the samples were analyzed in a computer. The repetition period (ms) and the maximum intensity (volt) was measured from the sound spectrogram and the amplitude envelope for each speech wave. Three acoustic parameters, which were mean of period (ms) (m-P), coefficient of variation of period (%) (CV-P), and coefficient of variation of amplitude (%) (CV-A), were calculated according to Ishida's acoustic analysis method. The average age in this study group was 52.4 +/- 11.4 years (32-73 years), the mean scores of International Cooperative Ataxia Rating Scale (ICARS) was 35.0 +/- 18.6. Significant correlation was shown between CV-A and ICARS scores before therapy (p < 0.05). CV-P was decreased significantly (p < 0.05) from 10.9 +/- 0.12% to 9.2 +/- 0.26% after TH, and its degree of decrement correlated with ICARS scores (p < 0.05), which means a greater effect of TH is expected in patients with milder symptoms. ICARS scores did not change with a statistical significance. TH was shown to be effective on the ataxic speech of patients with MJD by quantitative methods. The acoustic analysis used in this study is a sensitive and objective evaluation method for following up the clinical severity of MJD and judging effectiveness of a drug.