The noninvasive diagnosis of impaired mechanical integrity or compliance of the trachea is most accurately made by fluoroscopic observation recorded on video tape or cineradiography, with or without benefit of artificial contrast media (contrast tracheography). In particular, localized buckling, collapse or dilatation indicative of focal tracheomalacia may thus be diagnosed in vivo and correlated with diseases of the central airways. Congenital tracheomalacia is a rare, bu, well described entity. Cases of acquired tracheomalacia occur with increasing frequency, but are often not clearly recognized. We contrast the dynamic behavior of the normal trachea with the abnormal dynamics characteristic of focal tracheomalacia. Such lesions may result from trauma, surgical procedures, chronic irritation, inflammation, mechanical changes, or malignancy.