The treatment of atypical pneumonia, subsequently termed severe acute respiratory syndrome (SARS), is controversial, and the efficacy of corticosteroid therapy is unknown. We have evaluated the clinical and radiographic outcomes of 72 patients with probable SARS (median age 37 years, 30 M), who received ribavirin and different steroid regimens in two regional hospitals. Chest radiographs were scored according to the percentage of lung field involved. Seventeen patients initially received pulse steroid (PS) (methylprednisolone > or =500 mg/day) and 55 patients initially received nonpulse steroid (NPS) (methylprednisolone <500 mg/day) therapy. The cumulative steroid dosage; intensive care unit admission, mechanical ventilation, and mortality rates; and hematologic and biochemical parameters were similar in both groups after 21 days. However, patients in the PS group had less oxygen requirement, better radiographic outcome, and less likelihood of requiring rescue PS therapy than their counterparts. There was no significant difference between the two groups in hemolytic anemia, severe secondary infections, or hematemesis, but patients in the PS group had less hyperglycaemia. Initial use of pulse methylprednisolone therapy appears to be a more efficacious and an equally safe steroid regimen when compared with regimens with lower dosage and should be considered as the preferred steroid regimen in the treatment of SARS, pending data from future randomized controlled trials.