In a series of 2150 patients subjected to bronchoscopy 94 (4.5%) were found to have tracheobronchomalacia. Tracheomalacia alone was diagnosed in 21 patients (22%), tracheobronchomalacia in 59 (63%) and bronchomalacia alone in 14 (15%). Mild malacic changes were noted in 44 patients (47%), moderate in 38 (40.5%) and severe in 12 (12.5%). The main symptoms were dyspnoea (63%), chronic cough with expectoration (49%) and haemoptysis (33%), and the most frequent concurrent diseases chronic bronchitis (53%), bronchial cancer (27.5%) and pulmonary tuberculosis (19%). Bronchoscopy performed under local anaesthesia enabled the dynamics of the tracea and bronchi to be observed during spontaneous breathing and during coughing, and it is the best available diagnostic procedure. Histologically the number of longitudinal elastic fibres in the pars membranacea was clearly reduced throughout the whole tracheal area in one patient with tracheomalacia but no differences were found in the amount of collagen, mucopolysaccharides and elastin in the cartilages of trachea and bronchi. This disease seems to be associated with chronic obstructive pulmonary diseases such as chronic bronchitis, and it apparently shares the same aetiological factors.