Viscous (thick) sputum is a symptom of chronic diseases of the lower respiratory tract, which include bronchitis, congestive pneumonia, bronchial asthma, chronic obstructive pulmonary disease (COPD). Viscous sputum is characteristic of tuberculosis, cystic fibrosis, congenital and acquired bronchiectasis. To diagnose the cause of thick sputum, x-ray studies (CT, fluoroscopy, bronchography), endoscopic and functional methods are prescribed. Sputum analysis, standard blood tests are required. For treatment, mucolytics, anti-inflammatory, secretory agents, bronchodilators, antibiotics are used.