Many psychiatric studies of thyrotoxic patients have shown that long before the onset of clinical symptoms patients suffering from Graves' disease show emotional and psychosexual maladjustment. Preliminary observations in twenty-seven patients indicated a positive correlation between certain psychological variables and the occurrence of a short half-life of thyroidal I131, even in the absence of clinical signs of hyperthyroidism. Psychological studies of forty-four other patients were used to predict the type of biological decay of I131. The authors found that they could thus predict the rate of thyroid secretion with reasonable accuracy. No correlation was found between the activity of the thyroid gland and the degree of anxiety in these psychiatric patients. Thirty-eight 'stress interviews' were carried out, and no significant change in thyroid function due to stress was noted.