Cough is an important defensive reflex of the respiratory tract needed to clear and protect the airways; however, it may become exaggerated and interfere with quality of life. Chronic cough is one of the most common symptoms leading to referral to secondary or tertiary hospital. The purpose of this article is to review the most common causes of chronic cough and to provide a comprehensive algorithms for clinician in evaluating and treating the patient with chronic cough. After excluding the possibility of smoking, angiotensin converting enzyme inhibitor or other specific abnormality in chest radiography as a cause of chronic cough, upper airway cough syndrome (UACS), previously named as postnasal drip syndrome, asthma, nonasthmatic eosinophilic bronchitis (NAEB), and gastroesophageal reflux disease (GERD) are the most common causes of chronic cough and these conditions may be present alone or in combination. Chronic cough can be cured in most people by treatment of these underlying causes of chronic cough. (Korean J Med 76:252-259, 2009)