We conducted a multicentre, randomized, double-blind, placebo-controlled, parallel group study to determine the efficacy of controlled release salbutamol (SCR) tablets in clinically stable patients with predominantly non-reversible chronic airflow obstruction (CAO). Patients received either 8 mg SCR or matching placebo tablets twice daily for 6 weeks. Fifty-eight patients (30 on SCR and 28 on placebo) completed the study. Outcome measurements included FEV1, FVC, 6-min walking distance, and patient assessment of efficacy recorded at the clinic visits and twice daily PEFR measurements plus daytime symptom score recorded in diary cards. The absolute change between baseline and 6-week measurements with SCR was compared to that with placebo. Favourable trends were observed with SCR for all variables tested except FVC. The only significant difference between SCR and placebo was in FEV1 where there was a small net change of 95 ml in favour of SCR. We conclude, therefore, that the effects of lung function of long-term bronchodilator therapy with SCR in patients with stable non-reversible CAO are slight, and are likely to be of limited clinical benefit.