Persistent cough in children is a symptom, and the cause should be ascertained. Reactive airways disease is the most common reason for chronic cough in children over three to six months of age, especially at night. Under three months, the cause is likely to be more serious. Cough often disturbs parents more than the child, and physicians should consider parents' need for sleep and relief when deciding whether or not to prescribe cough suppressants. Investigations depend on the child's age, the history, duration and severity of the cough. A cause for the cough should always be sought.