Intensive personality studies were made of a group of 43 patients on whom sub-total thyroidectomy had been performed. The influence of social and psychologic factors on speed of fecovery was especially investigated. The patients were selected in such a way as to afford a representative sample of the clinic population. Each patient was given a psychiatric examination, the Wechsler-Bellevue Test, the Minnesota Multiphasic Personality Inventory, and a medical information and attitude scale. Thyroid disease occurs most frequently in middle-aged women. Lack of affection and security, broken homes and dominating mother characterized the childhood of patients with thyroid disease. An abrupt change to a different, more difficult environment was found to be a predisposing factor in precipitating thyroid disease. The female thyroid patients studied fell into 2 distinct groups : one with almost normal personalities; the other with reactions of an hysterical or anxiety type. Delayed recovery after operation was much more frequent in the thyroid group with hysterical and anxiety characteristics.