Cough is the most common complaint that leads patients to seek medical attention. Especially chronic persistent cough is annoying, and requires appropriate diagnosis and treatment. Recent cough guidelines and original papers on cough epidemiology from various countries show remarkable differences in the aetiology of chronic cough among countries, especially between US, UK and Japan. Entities associated with rhinosinus disease (post-nasal drip/upper airway cough syndrome reported from the US, rhinitis or rhinosinusitis from the UK, and sinobronchial syndrome from Japan), and eosinophilic lower airway disorders (cough variant asthma, non-asthmatic eosinophilic bronchitis and atopic cough) are most confusing and might involve significant overlap. In this article, issues related to chronic cough aetiology are discussed, including geographic issues, e.g. 'simple' geography or difference in race, and difference in patient characteristics possibly arising from difference in the medical system.