Single dose studies have assessed the utility of ipratropium bromide alone or with beta agonists in the short- and long-term management of chronic obstructive lung disease and asthma. We performed a randomized, double-blind trial to assess the incremental benefit over 24 hours of adding ipratropium vs placebo to a standardized regimen of medications commonly used in the acute and subsequent hospital management of COPD and asthma. Sixty-eight subjects received nebulized salbutamol, intravenous methylprednisolone, intravenous aminophylline, and antibiotics and were randomized to receive either 80 micrograms of ipratropium or placebo via metered dose inhaler and spacing device with each salbutamol treatment (6 to 8 times per day). Among the 50 patients who completed the study, there were no significant differences between ipratropium and placebo groups with respect to baseline FEV1, FVC, and PaCO2. The improvement of FEV1 from baseline to 24 hours was 294 (SD = 568) ml in the ipratropium group vs 393 (SD = 622) ml in placebo group. Adjusting FEV1 by age, gender, and smoking did not significantly alter the findings. Those with an admission diagnosis of asthma showed larger 24 hour FEV1 responses (487 ml in ipratropium vs 801 ml in placebo) than those with COPD (149 ml ipratropium vs 102 ml in placebo). However, within these two strata, there were no significant differences in FEV1 improvement between ipratropium and placebo groups. This study suggests that if ipratropium is used in the initial emergency treatment of COPD or asthma, it could safely be discontinued by 24 hours in order to reduce the cost and complexity of therapy.