A patient affected by low-frequency postural tremor of the trunk and limbs is reported. Apart from mild dysarthria and gait ataxia, no other neurological abnormalities were present. Cerebellar atrophy was demonstrated by means of magnetic resonance imaging. The tremor was associated with alternating activity in antagonistic muscles; it was triggered whenever a contraction of lumbar back extensor muscles occurred. Electrical stimulation of the cerebellum did not produce the normal suppression phases of motor responses evoked by a magnetic stimulation of the cerebral cortex.