Fahr's disease associates various degrees of neuropsychological impairment and calcium deposits in the basal ganglia. We report 3 cases. The first case was a 54-year-old man with hemichorea of one-year duration. Laboratory results demonstrated idiopathic hypoparathyroidism. In the second case, a 23-year-old man treated for epilepsia for 8 years was hospitalized for subintrant episodes and hemichorea. Dysmorphism and laboratory results led to the diagnosis of pseudo-hypothyroidism. The third case was a 62-year-old woman with generalized seizures of epilepsia and dementia of two-month duration. Physical examination revealed extra-pyramidal rigidity. Hyperparathyroidism due to an adenoma was confirmed histologically. In all three patients, correction of phosphocalcium levels led to clinical improvement, particularly with disappearance of the epileptic seizures and abnormal movements. Clinical expression of Fahr's syndrome varies greatly. Symptoms include psychiatric disorders, epileptic seizures, extra-pyramidal syndrome and various neurological conditions. Diagnosis requires CT brain scan which identifies calcium deposits in the basal ganglia. The main cause is hypoparathyroidism, whether primary or post-operative. Cases due to other causes of dysparathyroidism are rare. The pathophysiology of this condition remains unknown and results of treatment are often unsatisfactory. Since correcting the impaired calcium phosphorus metabolism often leads to considerable improvement, it is essential to systematically search for dysparathyroidism in patients presenting with neuropsychologic manifestations associated with calcifications of the basal ganglia.