We conducted a prospective, randomized, double-blind study to determine whether high-dose methylprednisolone could prevent parenchymal lung injury, including the adult respiratory distress syndrome (ARDS), or improve mortality when administered early in septic shock. All patients already hospitalized in or newly admitted to the medical and surgical intensive care units at San Francisco General Hospital between September 1, 1983 and August 29, 1986 were eligible for admission to the study if they had either (1) an increase in temperature of 1.5 degrees C and a decrease in systolic blood pressure of 20 mm Hg or more from baseline values (in already hospitalized patients), or (2) a temperature greater than 38.5 degrees C or less than 35.5 degrees C and a systolic blood pressure of less than 90 mm Hg (in newly admitted patients). Patients meeting these criteria were excluded if they (1) had severe immunodeficiency, (2) were less than 18 or greater than 76 yr of age, (3) had multilobar roentgenographic infiltrates, or (4) were already receiving corticosteroids. Eighty-seven patients enrolled in the study received either methylprednisolone, 30 mg/kg per dose, or mannitol placebo for a total of 4 doses every 6 h, following the presumptive diagnosis of septic shock. Of these patients, 75 ultimately were determined on the basis of culture results to have actually had septic shock at the time of entry. Thirteen of the patients who received methylprednisolone developed ARDS, compared to 14 patients who received placebo. Lesser degrees of parenchymal lung injury did not differ between the 2 groups.(ABSTRACT TRUNCATED AT 250 WORDS)