The aim of this study was to evaluate whether fluticasone propionate (FP) is effective as well as prednisone (P) in reducing sputum eosinophilia and in improving airway obstruction due to asthma exacerbations not requiring hospitalization. We measured, in a parallel-group, double-blind double-dummy, randomized study, sputum and blood inflammatory cell counts and soluble mediators in 37 asthmatic subjects during a spontaneous exacerbation of asthma (Visit 1) and after a 2 week (Visit 2) treatment with inhaled FP (1000microg bid) (Group A, n=18) or a reducing course of oral P (Group B, n=19). Asthma exacerbation was accompanied by sputum eosinophilia (eosinophils >2%) in almost all patients (95%). FP improved FEV(1) (from 53.9%+/-16.8 at Visit 1 to 76.4%+/-21.2 at Visit 2, p=0.0001) and reduced the percentage of sputum eosinophils (from 38%[0-78] to 3%[1-31, p=0.0008) as well as oral P (FEV(1): from 51.5%+/-14.4 to 83.6%+/-21.1, p=0.0001; sputum eosinophils: from 52%[1-96] to 11%[0-64], p=0.0003). At Visit 2, sputum eosinophils were significantly lower in Group A than in Group B. P but not FP induced significant decrease in blood and sputum ECP. Oxygen saturation, PEF variability, symptom score and use of rescue medication similarly improved in both groups. We conclude that FP is effective at least as well as P in reducing sputum eosinophilia and in improving airway obstruction due to asthma exacerbation. However, the cost/effectiveness ratio of this option should be further evaluated.