An animal model was used to study the effects of early administration of intramuscular corticosteroids on mortality and lung histopathology induced by a component of smoke. Thirty-six rabbits (mean weight, 2.7 kg) were exposed to acrolein vapor for 15 min; 30 min later the animals were divided into 3 treatment groups. One group received saline placebo intramuscularly at 12-h intervals, a second group was treated intramuscularly with 100 mg methylprednisolone at 12-h intervals, and a third group was treated with a single 100-mg dose of methylprednisolone followed by doses of saline at 12-h intervals. The animals were studied for a 72-h period. There was a significantly lower mortality in the 2 steroid-treated groups than in the nontreated group. A scoring system was developed for evaluating observed histologic changes in the lung. No correlation was seen between survival and histologic score or between score and treatment. High scores for particular histologic features did not explain mortality nor did they predominate in untreated animals; "vascular congestion" was found to be greater in the steroid-treated group. The beneficial effects of steroids in reducing mortality after inhalation of a common smoke constituent was not associated with any evidence of attenuation of lung damage.