The diagnostic dilemma Chronic cough is somewhat arbitrarily defined as any cough with a duration of eight weeks. It is common in primary care. In one postal survey of 11 000 patients registered with four general practices, 14% of men and 10% of women reported coughing on more than half the days in the year. In practice, smokers rarely consult about their cough because they assume (usually correctly) that smoking is the cause. Theproblem indiagnosis isdifferentiatingbetween the common causes of chronic cough—asthma, chronic obstructive pulmonary disease, postnasal drip, gastrooesophageal reflux disease (GORD), and drug (ACE inhibitor) induced—and not missing rare but more serious causes. In primary care the cause of chronic cough is often uncertain, and asthma is a common diagnosis. In a study in secondary care of 78 adult non-smokers with chronic cough and a normal chest x ray, in 73 (94%) the coughwas considered to be causedbyoneormore of the “pathogenic triad” of asthma, gastro-oesophageal reflux, and postnasal drip syndrome. In 48 patients (62%) there was more than one cause. Studies from specialist cough clinics found that the causeof chronic coughcanbeestablished in 89-100% of cases, making the previously popular diagnosis of “psychogenic cough” redundant. In smokers, chronic cough is common and can also be the presenting feature of chronic obstructive pulmonary disease or bronchogenic carcinoma.