Breathlessness is a common symptom in patients with primary bronchial carcinoma and is often not well-controlled. Most patients are ex- or current smokers, and therefore are at high risk for co-existing chronic obstructive pulmonary disease (COPD). The incidence of airflow obstruction in patients with bronchial carcinoma, its relation to breathlessness, and response to bronchodilator therapy was examined prospectively. Fifty-seven consecutive patients attending our outpatient clinic with bronchial carcinoma diagnosed in the preceding 12 months were studied (22 female, 35 male, mean age 68.4 years). Spirometry was performed and breathlessness rated. Those with airflow obstruction (FEV1:FVC < 65% and FEV1 < 70% predicted) and who judged themselves to have moderate or severe breathlessness, were offered a trial of bronchodilator therapy. The response to regular inhaled fenoterol and ipratropium bromide by metered dose inhaler (MDI) and large volume spacer, and to regular nebulized salbutamol and ipratropium bromide was assessed by home peak flow recordings, spirometry and two subjective scores: (a) rating of breathlessness on a simple four-point scale, and (b) activity score of the St George's Respiratory Questionnaire. There was very strong association between airflow obstruction and breathlessness. Twenty-eight patients (49%) had airflow obstruction, and we had breathlessness ratings on 26 of these patients of whom 18 (69%) had rated it as moderate or severe. Only four of the patients with airflow obstruction and breathlessness were using bronchodilator therapy. There was no significant difference in the mean age, time from diagnosis, tumour site, or smoking history between the groups with, and without, airflow obstruction. There was no association between cell type and the presence of airflow obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)