The optimal amount of systemic corticosteroids to be used in acute severe asthma remains an unresolved issue. In this double-blind, randomized study we compared two doses of methylprednisolone (1 vs 6 mg.kg-1 q.d.) in asthmatics presenting with an acute severe asthma attack, unresponsive to an intensive beta 2-agonist regimen administered during a run-in period. Concurrent therapy, including oxygen, inhaled and intravenous salbutamol, and aminophylline was strictly standardized. The response was assessed by serial bedside spirometry. The primary outcome measurement was forced expiratory volume in one second (FEV1) (expressed as percentage of predicted values) at 24 and 44 h. The trial was designed in order to achieve a statistical power of 90%. Twenty three patients were included in the low-dose group and 24 in the high-dose group. Both groups were comparable in terms of demographic profiles, history of asthma, and severity of the current attack. Improvement in pulmonary function was similar in both groups. At 44 h, the mean (+/- SD) FEV1 values were 53 +/- 22 and 45 +/- 14% in the low and in the high-dose group respectively (NS). We conclude that high dose systemic corticosteroids offer no further benefit over low-doses in the treatment of severe acute asthma.