SummaryThe authors have observed a woman, 56 years old, with multiple adenomata of the parathyroid glands.The patient underwent parathyroidectomy at three times from deoember 1945 to July 1946, each of these explorations permitted to remove a parathyroid adenoma. Histological pictures of the three glands were very different : adenoma with big wasser-clear cells, tubular or alveolar formations, adenoma of the type said“endocrine adenoma”were found, sometimes in the same gland. Removal of the 3 adenomata corrected only partially the humoral picture ol the disease. Radiologically, no change was observed. It must ho pointed out that each of the surgical explorations did only show one adenomatous gland and it seems likely that the 2 adenoma removed afterwards developed after the first operation was performed.Excretion of P by the kidneys was used as a test of parathyroid activity in this case. The low phosphorus serum level was increased by intravenous administration of phosphates. Filtration rate was appreciated by the clearance of endogenous creatinine. The levels of excreted P were plotted against plasma levels and compared with those of 19 normal people studied by the same procedure. It was noted that the renal excretion of P in this patient was much higher than that of normal people. This was true not only at normal blood levels, but also when the blood concentration was increased enough to saturate the maximal capacity of the tubules to reabsorb phosphates.This observation does not agree with the conclusions of Jahan and Pitts who consider that parathyroid extracts do not change the maximal capacity of the renal tubules to reabsorb phosphorus.Removal of the first adenomatous gland was followed by a dicreased excretion of phosphates. The two last operations were only followed by a slight change in the renal function : a fact suggesting the persistanee of another adenomatous gland, perhaps in the neighbourghood of the thymus.