SummaryHypocalcemia may complicate osteoblastic metastases. The study of parathyroid status in these cases gave discrepant results. A patient with asymptomatic hypocalcemia and breast cancer is described. Immunoreactive parathormone was inappropriately low in the basal state and after sodium EDTA infusion. Parathyroid failure could have been idiopathic, secondary to parathyroid metastases or, less likely, to external irradiation.