Mucus hypersecretion (greater than 25 ml/day) is commonly seen in chronic bronchitis, whereas bronchorrhea (greater than 100 ml/day) is found in other conditions (e.g. asthma, bronchiectasis, alveolar-cell carcinoma). Clearance of secretions can be improved by physical and pharmacological methods. Cough airways obstruction--for "two-phase air-liquid flow". Chest physiotherapy (the forced expiration technique, FET, and postural drainage, PD) is effective in clearing central and peripheral secretions and can be self-employed. Oral high frequency oscillation (OHFO) at 13 Hz is a useful adjunct. Beta-adrenergic drugs improve clearance and this is not entirely to their bronchodilator activity. Likewise methylxanthines enhance clearance particularly in central airways. Corticosteroids are effective in bronchorrhoea and asthma. Anticholinergics may control hypersecretion. Mucolytics and expectorants are used traditionally but their activity is difficult to prove. Hypertonic (7%) saline is useful--as is cromoglycate in asthma.