Acquired tracheobronchomalacia is seen in middle-aged and elderly people. Weakness of the tracheal and bronchial walls allows the posterior and anterior walls to draw nearer together during expiration and coughing, producing a varying obstruction. The main symptoms are dyspnoea, cough, phlegm and haemoptysis. Tracheobronchomalacia has often been diagnosed as chronic bronchitis, and the dyspnoea has also been treated as asthma, without success. Bronchoscopy, cineradiography, spirometry and intrabronchial pressure measurements are the diagnostic methods used. Tracheobronchomalacia is a progressive condition and must be taken into account in the diagnosis of obstructive pulmonary diseases and in the assessment of the working capacity of dyspnoeic patients. Treatment is preventive and symptomatic; in selected cases surgery also may be of benefit.