A patient is described who 32 years after thyroidectomy developed a chronic progressive syndrome due to hypoparathyroidism, with multiple extrapyramidal signs (faciobuccolingual dyskinesias, choreiform and athetotic movements of upper extremities, tremor of hands, cogwheel phenomenon), cerebellar manifestations (dysarthria, dysgraphia, mild gait ataxia), and pyramidal signs as well as an organic psychosis and epilepsy. A CT scan showed calcification of the basal ganglia. Therapy for hypoparathyroidism produced partial regression of the disorder. To explain the physiopathologic mechanism of the syndrome, Selye et al. advanced an attractive hypothesis of calciphylaxis, which assumes that a sensitizer and a challenger together induce development of calcification. In the case reported calcification involved the periventricular region and was not limited to the basal ganglia. It is suggested that either a sensitizer or a challenger may enter the periventricular tissue via the ependyma.