The author experienced remarkable effects of Gynergen (Sandoz) in two cases of heartfailure after thyroidresection in Basedow's disease. Case 1. When the pulse of the patient became weak and frequent and the general condition was getting more serious after the operation, the author injected Gynergen (Sandoz) hypodermically, and found the quick improvement of the conditions both subjectively and objectively. Case 2. This case was a typical form of the vagotonic exophthalmic goitre after Eppinger and Haas in which goitre, cardiac disturbances, increased perspiration and chronic diarrhoea in long period were chief complaints without noticiable exophthalmos. The author performed thyroidresection when the basal metabolism was lowered by iodine treatment. Two days after the operation the irregular pulse was seen temporarily, but recovered by injection of Gynergen. On the fourth day after the operation suddenly appeared the symptom of socalled “Coma Basedowicum Zondek” and heart became quite out of order showing auricular fibrillation, perpetual arhythmia, ventricular and auricular extrasystole, and never recovered until death followed even by injections of Gynergen, physostigmin, quinine derivatives and other cardiacs and also blood transfusion as well. As an imoirtent factor of causal conditions of “Coma Basedowicum Zondek” the author believes that the changes of heart due to intoxication by thyroidsubstance play a Principal role. That is to say, the operative manipulation results easily temporary increase of thyroidsubstance in blood vessels, and the balance of metabolism may be broken, and on the other hand the disturbances of blood circulation of whole body due to the changes of heart accelerate the development of serious comatose condition like bulbar paralysis and lead to death. Observing the remarkable effect of Gynergen on the tachycardia and arhythmia after thyroidresection in Basedow's disease, the author recommends the clinical application of it in such cases.