Twenty-four elderly male patients with moderate-to-severe chronic airway obstruction took part in a double-blind, placebo-controlled, randomized dose-response and response-duration comparison of a new inhaled anticholinergic bronchodilator oxitropium bromide and the inhaled beta-agonist bronchodilator fenoterol hydrobromide. On 6 separate days lung function changes and side effects were monitored for 8 h after either placebo, oxitropium 100, 200 and 300 μg, fenoterol 400 μg, or oxitropium 200 μg plus fenoterol 400 μg. Fenoterol alone and in combination with oxitropium produced a rapid peak effect (mean ΔFEV1= 41.6 and 39.5%, respectively at 30 min). Oxitropium alone had a slow onset of action (peak ΔFEV1 seen at 120 min: 100 μg = 22.7%, 200 μg = 29.9%, 300 μg = 28.2%). However, mean FEV1 remained within 5% of peak for 60 min after fenoterol, but for 180 min after each dose of oxitropium and after fenoterol plus oxitropium. No differences between oxitropium 200 and 300 μg were seen; however, these doses produced more prolonged bronchodilatation than did oxitropium 100 μg. The fenoterol-plus-oxitropium combination produced even more prolonged bronchodilatation. The only side effect, seen with each inhaler was a mildly unpleasant taste. No anticholinergic effects were seen. We conclude that oxitropium is an effective bronchodilator with slow onset but prolonged duration of action. In combination with fenoterol it produced both rapid and prolonged bronchodilatation in patients with chronic airflow obstruction.