We describe three patients with unilateral asterixis. One diabetic patient with a moderately-sized haematoma in the left putamen initially developed bilateral and symmetrical asterixis, which became confined to the right side as his diabetes mellitus was controlled. Two patients showed unilateral asterixis due to haematomas in the contralateral basal ganglia and thalamus, respectively. The present findings indicate that not only lesions of the thalamus but also those of the basal ganglia can cause unilateral asterixis, and bilateral and symmetrical asterixis does not necessarily exclude the presence of a focal mass lesion in the cerebrum.