Hyperbaric Oxygen Therapy is an important treatment in cerebral ischemia caused by cerebrovascular diseases. In this experimental study, ten rabbit brains with cerebral ischemia were treated with Hyperbaric Oxygen under 2 atm. pressure, and the histopathological findings compared with those of a control group. We demonstrate that Hyperbaric Oxygen Therapy has a considerable effect both in reducing edema and in preventing micronecrosis and macrocyst formation in ischemic brain tissue.