Hemichorea-hemiballism (HCHB) is an usually continuous, nonpatterned, involuntary movement disorder caused by basal ganglia dysfunction, commonly due to a vascular lesion, described in nonketotic hyperglycemic patients. Particular computed tomography and magnetic resonance imaging findings have been described. The pathogenic mechanism of chorea arising during hyperglycemia and the nature of neuroimaging findings are unclear. In this paper we describe two elderly women with onset of HCHB during a hyperglycemic episode. The symptoms persisted in one of them after recovery of normal glycemia. The pathophysiological mechanism of the disease is discussed in the light of clinical and neuroradiological follow-up.