Nebulized budesonide has been used successfully to treat acute asthma exacerbation, and we hypothesized that it could also be effective for exacerbations of chronic obstructive pulmonary disease (COPD). In this multicenter, double-blind, randomized, placebo-controlled trial, the efficacy of nebulized budesonide (Pulmicort Respules/Nebuamp), oral prednisolone, and placebo was compared in 199 patients with acute exacerbations of COPD requiring hospitalization. Patients received from randomization (H(0)) to 72 h (H(72)), 2 mg of budesonide every 6 h (n = 71), 30 mg of oral prednisolone every 12 h (n = 62), or placebo (n = 66). All received standard treatment, including nebulized beta(2)-agonists, ipratropium bromide, oral antibiotics, and supplemental oxygen. The mean change (95% confidence interval) in postbronchodilator FEV(1) from H(0) to H(72) was greater with active treatments than with placebo: budesonide versus placebo, 0.10 L (0.02 to 0.18 L); prednisolone versus placebo, 0.16 L (0.08 to 0.24 L). The difference in FEV(1) between budesonide and prednisolone was not significant, -0.06 L (-0.14 to 0.02 L). The occurrence of serious adverse events was similar for all groups. Budesonide had less systemic activity than prednisolone as indicated by a higher incidence of hyperglycemia observed with prednisolone. Both budesonide and prednisolone improved airflow in COPD patients with acute exacerbations when compared with placebo. Nebulized budesonide may be an alternative to oral prednisolone in the treatment of nonacidotic exacerbations of COPD but further studies should be done to evaluate its long-term impact on clinical outcomes after an initial episode of COPD exacerbation.