The clinical maxim that the anteroposterior (AP) diameter of the chest is increased in patients with advanced pulmonary emphysema was tested. Various dimensions of the thorax were compared in 25 hospitalized patients with emphysema characterized by dyspnea, hyperinflation of the chest determined by roentgenogram, and reduced vital capacities and decreased rates of expiratory air flow; 22 patients with other diseases, and 16 normal subjects. The expiratory AP diameters were 23.0, 22.3, and 20.2 cm, respectively; the corresponding inspiratory AP diameters were 24.4, 23.5, and 23.3 cm. The differences were not significant. Therefore, it is concluded that decreased diameters of the abdomen due to decreased body weights make the AP diameters of the chest appear to be increased when, in fact, they were not different from normal.