ABSTRACT Three patients with atypical, intermittent tetany of recent origin, hypocalcaemia, hypocalciuria and normal serum inorganic phosphorus concentration are described. Two patients were postoperative from thyroidectomy by more than 20 years and one had recently experienced metastatic malignant invasion of the thyroid area. A variety of studies showed that these patients were neither normal nor typically hypoparathyroid in the laboratory. Two hypotheses, each with some support are: 1. that the patients were not totally aparathyreotic, and 2. that, while aparathyreotic, they had adapted to the abnormal state by some mechanism operative in the absence of parathyroid hormone.