Thyroid-function tests were performed on one hundred patients with suspected premyxoedema and the results compared with those in twenty age and sex matched controls. The increase in thyroid-stimulating hormone (T.S.H.) in response to thyrotrophin-releasing hormone (T.R.H.) was exaggerated in eighty-eight of the hundred patients with suspected premyxoedema. These included twenty-five with normal basal T.S.H. and sixty-three with a raised basal T.S.H. Serum-cholesterol concentration was significantly higher in those in whom premyxoedema was suspected than in the controls, even when patients presenting with degenerative arterial disease were excluded.