Persistent or chronic cough is defined as a cough lasting more than 3 weeks. A systematic approach to the diagnosis and treatment of chronic cough involves a detailed history. The age of the child, descriptive qualities of the cough, and environmental exposures are particularly important. A thorough physical examination, looking for evidence of growth retardation and failure to thrive in addition to more specific signs, is essential. When further investigation is necessary, a complete blood count, chest radiograph, and PPD are indicated. Additional testing is guided by findings in the history and physical examination to rule out the less common but more serious causes.