To the Editor.— I wish to call attention to an article from the British Journal Medical that was abstracted in the February 14 issue of the Journal of the American Medical Association (237:705, 1977): A black thyroid has not been reported in man, but has been found in monkeys, dogs, and rats during trials with minocycline. A uniformly black thyroid was found in a 69-year-old man who died in respiratory failure from bronchiectasis and emphysema. . . . The monofluorescent pigmentation of the thyroid is attributed to the specific concentration of minocycline in the thyroid and increased lipofuscin deposition. Because previous experimental studies with minocycline have demonstrated an antithyroid effect, patients receiving prolonged minocycline therapy should have their thyroid function monitored. Do those of us who prescribe minocycline for acne now need to monitor thyroid function?