In a recent multicenter randomized controlled trial, prolonged administration of low-dose methylprednisolone (1mg/kg/day) initiated in early acute respiratory distress syndrome was associated with earlier resolution of pulmonary and extrapulmonary organ dysfunction and reduction in duration of mechanical ventilation and intensive care unit stay. However, glucocorticoids may induce serious adverse events and these adverse events might compensate the positive effect of prolonged methylprednisolone infusion and discourage physicians from treating acute respiratory distress syndrome patients with glucocorticoids. Early prediction of responsiveness to prolonged methylprednisolone infusion would be help to decide whether to continue or not prolonged methylprednisolone infusion and this could reduce the drug related adverse events. We project to evaluate the predictors of responsiveness to prolonged methylprednisolone infusion in early acute respiratory distress syndrome .