Twelve male patients with radiological evidence of pulmonary emphysema performed progressive exercise tests on a cycle ergometer. Ipratropium bromide (Ip) 40 micrograms, Fenoterol (Fen) 400 micrograms, their combination (Ip/Fen) and Placebo were administered from metered-dose inhalers in a double-blind crossover study to compare the effects on ventilation (VE), heart rate (fc) and oxygen uptake (VO2) at rest and at maximal and sub-maximal workloads. There were no significant differences in resting VE (p greater than 0.05) between the 4 treatment regimes. During submaximal exercise, VE at a given workload was greater after Fen containing treatment regimes than after Ip alone or placebo. There was no significant difference in the maximal workload achieved after the active treatments compared with placebo. With respect to fc and VO2, there were no differences between treatments at rest or on submaximal or maximal exercise. Fenoterol produces a mild stimulation of VE during exercise as observed with other beta-agonists, but compared with the changes in resting vital capacity, functional residual capacity and residual volume, the bronchodilator induced changes in exercise variables were relatively small.