The clinical significance of evaluating autonomic nervous system functions in the early stages of olivopontocerebellar atrophy (OPCA) has been investigated in 13 OPCA out-patients (7 males and 6 females, mean age: 51.0 years). We have employed measurements of blood pressure, plasma norepinephrine (NE), CVR-R, low-frequency power/high-frequency power ratio (L/H), high-frequency power (HF) score and heart rate (HR) monitoring using Holter ECG recording for evaluation of CVR-R. We have also carried out urodynamic examinations, focusing on the possible existence of bladder dysfunction. Although no significant changes were noted between control and OPCA groups concerning HR, CVR-R, L/H, plasma levels of norepinephrine and systolic blood pressure, HF (high-frequency power) (ms(2)), especially at night time, invariably showed a significant decline in OPCA groups. All OPCA patients who showed a decreased circadian HF also exhibited a tendency towards urinary bladder dysfunction. The present results appear to relate to disorder of the parasympathetic autonomic nervous system and neuromuscular dysfunction in the lower urinary tract. In conclusion, HRV (heart rate variability) analysis is a useful and safe tool and a keen predictor for evaluating functional states of autonomic nervous activity, especially in the early stages of OPCA. This study has also suggested the possible efficacy of urodynamic measurements in OPCA patients as an indicator of neuromuscular dysfunction in the lower urinary tract and of parasympathetic malfunction.