Follow-up examinations at regular intervals to recognize trauma-induced lesions are as essential for persons who have suffered a chest trauma as they are for cases of injury to the limbs. A classification into three groups according to the number of broken ribs relates satisfactorily with thoraco-pulmonary complications and residual damage. Injuries in group 1 leave practically no permanent damage; in group 2 they are apt to be followed by residual respiratory impairment while in group 3 the likelihood of permanent impairment of lung function is very high. Spirometry, roentgenography and fluoroscopy, and lung scanning are of special diagnostic value in assessing late sequelae of multiple rib fractures. Gas analyses are of little value. They would provide more accurate information if performed during exercise under standard conditions.