INTRODUCTION During a general course of study on the syndrome of the so-called "irritable heart of soldiers," investigation was made into the frequently alleged relationship of this disorder to hyperthyroidism. Among other methods of examination employed in the study was the epinephrin reaction as used by Goetsch.1He reports that patients with hyperthyroidism are hypersensitive to epinephrin in that following the injection of the drug a much greater response is obtained than is the case in normal individuals. This response consists in a rise of bloodpressure and pulse rate, and the production of certain characteristic symptoms. In the investigation at General Hospital No. 9 on patients showing the symptom complex of the "irritable heart of soldiers," it has been found that a considerable percentage of these cases are also hypersensitive to the drug. Careful clinical analysis, however, as well as determinations of the basal metabolism, do not lend any support