Lung volume reduction surgery (LVRS) improves dyspnoea and pulmonary function in selected patients with severe emphysema. The purpose of this study was to assess the effects of LVRS on exercise performance and gas exchange in relation to changes in pulmonary function. In 40 patients (63.2+/-1.4 yrs, mean+/-SE) with severe emphysema (forced expiratory volume in one second (FEV1) 29+/-1% predicted, residual volume/total lung capacity (RV/TLC) ratio: 0.63+/-0.01) we assessed dyspnoea, pulmonary function and exercise performance before and 3 months after bilateral video-assisted thoracoscopic LVRS. The Medical Research Council dyspnoea score fell from 3.5+/-0.1 to 1.4+/-0.1 (p<0.0005); FEV1 increased by 55+/-9% to 44+/-2% pred (p<0.0005), RV/TLC decreased from 0.63+/-0.01 to 0.51+/-0.02 (p<0.0005). The diffusing capacity remained unchanged. Maximal work load during bicycle ergometry increased from 34.3+/-2.0 to 48.9+/-2.4 W (p< 0.0005), maximal oxygen uptake (V'O2max) from 10.0+/-0.4 to 12.8+/-0.3 mL x kg(-1) x min(-1) (p<0.0005). The increase in maximal ventilation during exercise (V'Emax) from 29.5+/-1.5 to 38.6+/-1.8 L x min(-1) (p<0.0005) was associated with increases in tidal volumes at isowatt and maximal exercise while corresponding breathing frequencies remained unaltered. The increases in V'O2max and V'Emax correlated with the increases in FEV1 and the decreases in RV/TLC. We conclude that the improvement in pulmonary hyperinflation and airflow obstruction after bilateral thoracoscopic lung volume reduction surgery may reduce ventilatory limitation, thereby increasing exercise capacity.