Astasia, which is the inability to stand in the absence of motor weakness or marked sensory loss, is an uncommon clinical feature of stroke in the thalamic ventrolateral region. The authors describe a patient with a unilateral supplementary motor area (SMA) infarction presenting with contralateral astasia. On neurological examination, he would lean to the left side and would fall unless supported. He showed no muscle weakness, sensory deficits or cerebellar ataxia. Magnetic resolution imaging of the brain showed acute infarction only involving the right SMA. On the basis of the anatomy that the SMA is connected to the vestibulocerebellar system through the ventrolateral nucleus of the thalamus, the authors concluded that contralateral astasia probably resulted from disruption of this connection following infarction of the SMA.