To evaluate autonomic function in sporadic cases of cerebellar degeneration (CD) with or without mild autonomic dysfunction, we measured muscle sympathetic nerve activity (MSNA) by microneurography in 12 CD patients and 18 healthy subjects. The burst incidence and mean amplitude of MSNA at rest was significantly decreased in CD patients (P < 0.01). There were no significant differences between patients with CD and controls in heart rate or blood pressure at rest. During head-up tilting, increases in blood pressure and mean amplitude of MSNA were significantly lower in CD patients. In conclusion, a decrease in muscle sympathetic outflow can be observed even in CD patients who are clinically excluded from multiple system atrophy (MSA). It might be difficult to distinguish other CD syndromes from MSA in recordings of muscle sympathetic activity.