The part assigned to me in this symposium is the diagnosis of this remarkable disease. What I shall have to say is based (1) on an analysis of the cases which have occurred in my wards at the Johns Hopkins Hospital during the past two years,<sup>1</sup>and (2) on a study of the bibliography of the subject.<sup>2</sup> It will be convenient to discuss (I) the character and significance of the individual signs and symptoms; (II) the diagnosis of the clinical syndrome, especially in its less obvious forms; (III) certain points in differential diagnosis, and (IV) the diagnosis of the indications and contraindications for surgical interference. On account of the necessity of brevity I am forced to limit the discussion to the features which I regard as most essential. <h3>I. THE CHARACTER AND SIGNIFICANCE OF THE INDIVIDUAL SIGNS AND SYMPTOMS.</h3> Besides the three cardinal symptoms—struma, tachycardia and exophthalmus—there are