The degree of acute improvement in spirometric indices after bronchodilator inhalation varies among chronic obstructive pulmonary disease (COPD) patients, and depends upon the type and dose of bronchodilator and the timing of administration. Acute bronchodilator responsiveness at baseline was examined in a large cohort of patients with moderate-to-very-severe COPD participating in the Understanding Potential Long-term Impacts on Function with Tiotropium (UPLIFT) trial, a 4-yr randomised double-blind trial evaluating the efficacy of 18 mug tiotropium daily in reducing the rate of decline in lung function. After wash-out of respiratory medications, patients received 80 mug ipratropium followed by 400 mug salbutamol. Spirometry was performed before and 90 min following ipratropium administration. The criteria used for forced expiratory volume in one second (FEV(1)) responsiveness were: >or=12% increase over baseline and >or=200 mL; >or=15% increase over baseline; and >or=10% absolute increase in the percentage predicted value. Of the patients, 5,756 had data meeting the criteria for analysis (age 64.5 yrs; 75% male; baseline FEV(1) 1.10 L (39.3% predicted) and forced vital capacity (FVC) 2.63 L). Compared with baseline, mean improvements were 229 mL in FEV(1) and 407 mL in FVC. Of these patients, 53.9% had >or=12% and >or=200 mL improvement in FEV(1), 65.6% had >or=15% improvement in FEV(1), and 38.6% had >or=10% absolute increase in FEV(1) % pred. The majority of patients with moderate-to-very-severe chronic obstructive pulmonary disease demonstrate meaningful increases in lung function following administration of inhaled anticholinergic plus sympathomimetic bronchodilators.