Symptoms, clinical findings and pulmonary function in 47 patients with tracheobronchomalacia were compared with the bronchoscopic finding. The main symptoms were phlegm, cough, and dyspnoea. Recurrent respiratory infections and haemoptysis were features of the recent medical history. Only 30% had emphysema, and cor pulmonale in the ECG was uncommon. A notch in FEV1 was seen in 25 patients (54%), against 3 (6%) in the controls. FVC, FEV1/FIV1 and notch in FEV1 were directly proportionate to the severity of the malacia. A low FEV1/FIV1 and notch in FEV1 are suggestive of tracheobronchomalacia and an indication for bronchoscopy.