BACKGROUND: Although it is the commonest symptom presented to general practitioners (GPs), little is known about why someone decides to consult with a cough. AIM: To describe the illness behaviour of patients with a cough. METHOD: Patients who had consulted a GP because of a cough, and a group of subjects who had recently had a cough but had not consulted, were interviewed in a qualitative study that investigated how they made sense of their illness. RESULTS: Consulting patients understood their cough to be abnormally severe, whereas non-consulting subjects regarded their cough as 'normal' and mild. Consulting patients thought the cough would interfere with social roles and non-consulting subjects did not. The consulting patients were much more likely to be worried about the cough than the non-consulting subjects. In particular, half of the consulting patients were worried about their hearts, whereas the non-consulting subjects were not. The two groups did not distinguish bacteria from viruses, and did not differ in beliefs about the role of antibiotics that they thought were needed for severe coughs. Both groups had concerns about pollution. CONCLUSIONS: For consulting patients, cough breached the taken for granted property' of health that the non-consulting subjects with a cough were able to maintain. Cough, for the consulting patients, was not a trivial illness.