The present article is chiefly concerned with those thyroid abnormalities which have been found associated with the so-called affective psychoses. The author himself has met with many cases of melancholia, hypomania, and anxiety psychosis, which, at the same time, were goitrous. Thus in a case of agitated melancholia presenting thyroid enlargement with signs of hyperthyroidism, complete mental recovery followed the removal of a thyroid cyst. In another case of melancholia with a large goitre the latter was treated by radio-therapy, with the result that the signs of hyperthyroidism diminished and the melancholia disappeared.