The tongues of two patients with macroglossia were examined at autopsy. One of the patients had acromegaly and the other had hypothyroidism. To evaluate the size of the enlarged tongues, the average weight of the tongue in the human adult was determined first in a series of 20 unselected autopsies, 10 males and 10 females (ages 44 to 85). The weight of the tongue was greater in males than in females and was directly correlated with the height of the subject. Cachexia had relatively little effect on the weight. In acromegaly (case 21) and myxedema (case 22) the tongue was enlarged by at least 50%. Histopathology showed enlargement of muscle fibers especially anteriorly in acromegaly and hypothyroidism, thickening of the epithelium and increased subepithelial and interstitial connective tissue. Incidental findings included venous thrombi and telangiectasia in the subepithelial connective tissue in both hypothyroidism and acromegaly and a corpus amylaceum and two islands of hyaline cartilage in the tongue of hypothyroidism.