There appears to be no general agreement with respect to the efficacyof the parathyroid hormone in the absence of the kidneys. The indications of the inessentiality of the kidneys in the parathyroid control of serum calcium (Ellsworth and Futcher, 1935; Stoerk, 1943; Monahan and Freeman, 1944) have not been fully confirmed (Tweedy et al., 1937; Neufeld and Collip, 1942). On the other hand, Albright and Reifenstein (1948) are of the opinion that “the main action of the parathyroid hormone is to increase phosphate excretion in the urine.” Greep (1948) in his comprehensive review has probably summed up the situation correctly and concisely in his statement that “a true hypercalcemia has never been produced in such an animal” (i.e., in a nephrectomized animal) although he emphasized the adverse biochemical changes resulting from such an operative procedure. Implicit in his statement is the uncertainty regarding the extent of the response elicited by the hormone in the absence of the kidneys.