Two female spayed dogs belonging to the same owner were admitted for further examinations because of clinical signs and laboratory values compatible with hyperthyroidism. Sonography of the ventral aspect of the neck revealed small thyroid glands in both dogs. The hypothesis that the dogs suffered from alimentary hyperthyroidism caused by feeding head meat containing thyroid gland tissue was confirmed by consultation of the slaughtering plant, determination of iodine concentrations in deep-frozen samples and hormone measurements in 5 other dogs receiving head meat from the same supplier. After changing the diet, thyroxine concentrations declined and clinical signs were no longer observed.