Measurements on standard frontal and lateral radiographs that reliably predict the presence or absence of chronic obstructive lung disease would be useful to the clinical radiologist when no other clinical data are available. Therefore, statistical correlations of pulmonary function tests and measurements of chest films were made in 104 men chosen from 1000 cases referred for pulmonary function tests in whom no obvious abnormality was present on the chest film. Two measurements were significantly correlated (p less than 0.001) without requiring correction for body surface area: (1) The height of the arc of the right diaphragm in the lateral projection. When 2.6 cm or less it identifies 67.7% of all patients with abnormal pulmonary function tests and 78.3% of patients with moderately or severely abnormal pulmonary function tests. (2) The height of the right lung in the posteroanterior projection. When this is 29.9 cm or more it will identify 69.8% of all patients with abnormal pulmonary function tests and 79.7% of patients with moderately to severely abnormal pulmonary function tests. These simple measurements will assist the radiologist to judge from standard chest radiographs whether a patient may or may not have chronic obstructive lung disease.