IN 1951, it was shown at this College that eight out of a total of fourteen ewes, fed upon a diet of linseed meal, oats and lucerne hay, produced lambs with acute goitre. This work has been repeated, and once again lambs with enlarged thyroids have been produced. These glands showed a reduced percentage iodine content, compared with control animals kept under similar conditions. The addition of potassium iodide or di-sodium L-thyroxine to the drinking water was found to be prophylactic. Evidence for this was provided by both chemical analysis and histological examination of the thyroids concerned.