Blood in sputum, haemoptysis, is a common symptom in mucous membrane disorders of the respiratory tract--it is often seen in conjunction with inflammation but may also be associated with malignant tumours of the respiratory tract. In a survey of 422 patients with monosymptomatic haemoptysis, 15 patients with bronchogenic carcinoma were identified. A cytological examination of the sputum of these 15 patients was carried out, and in 9 of these cases suspected malignant cells were observed. From these and other observations it is concluded that with patients of over 40 years of age who are smokers with haemoptysis, but who display a normal X-ray examination of the thorax, it would be prudent to carry out a cytological examination of the sputum before bronchoscopy.