The objective of this study was to determine the effect of steroid therapy on pulmonary function, admission rates, and relapse rates in patients presenting with acute exacerbations of asthma. Computerized MEDLINE and SCIENCE CITATION searches were combined with review of reference lists from book chapters and articles to identify published randomized trials on steroid interventions. Over 700 articles were reviewed by two independent reviewers who identified 30 relevant randomized controlled trials for analysis. Study validity was independently assessed by two reviewers and information regarding populations, interventions, and outcomes was abstracted. Binary outcomes were combined and reported as odds ratios (OR), using the Mantel-Haenszel method. Individual and pooled effect sizes (ES) were determined for pulmonary function data. The authors found that the use of steroids early in the treatment of asthmatic exacerbations reduces admissions in adults (common OR 0.47; 95% confidence interval (CI) 0.27, 0.79) and children (OR 0.06-0.42). They found steroids effective in preventing relapse in the outpatient treatment of asthmatic exacerbations (OR 0.15; CI 0.05, 0.44). Oral and intravenous steroids appear to have equivalent effects on pulmonary function in acute exacerbations (ES -0.07; CI -0.39, 0.25). The authors conclude that overall, steroid therapy provides important benefits to patients presenting to emergency departments with acute exacerbations of asthma. Further research into dosage, alternative routes of administration, and alternative outcome measures is needed.