In a double-blind study, the effect of high doses of methylprednisolone on the cerebral edema induced by cerebral infarction was evaluated in 76 Mongolian gerbils. The incidence of experimentally induced cerebral infarction following carotid artery ligation is high in these animals because they lack a posterior communicating artery. One hour after the left common carotid artery had been ligated, 34 animals were given 30 mg per kilogram of the adrenocorticosteroid and the dose was repeated 24 and 48 hours later. Thirty-four animals were given normal saline on the same treatment schedule. Eight animals with sham operations were not treated. The animals were observed for ten days for signs of stroke. Surviving animals were killed on the tenth day and all brains were examined macroscopically and microscopically. Stroke developed in 41% of all animals; 31% died within ten days. Of the steroid-treated animals, stroke developed in 38% and 26% died. Of the saline-treated animals, stroke developed in 44% and 35.5% died. The differences were not significant by chi square analysis and the authors concluded that large doses of methylprednisolone given one hour after carotid ligation failed to prevent or influence the course of experimental stroke.