✓ Although the beneficial effects of glucosteroids on brain edema are well documented and generally accepted clinically, investigations into their effects on experimental brain edema have been somewhat contradictory. In this study brain edema was produced by local cortical freezing in animals pretreated with glucosteroids and in untreated animals. Gross estimation of edema, wet weight-dry weight determination, and mechanical planimetry of areas of extravasated dye indicated a statistically significant reduction in edema of both white and gray matter at 24, 48, and 72 hours. Gross estimation of edema indicated a persisting effect with resolution of edema at 5 days in treated animals and from 7 to 12 days in untreated animals. These studies substantiate initial investigations and indicate a primary reduction in brain edema by glucosteroids. At least one of the effects of the glucosteroids appears to be reduction of the abnormal vascular permeability causing brain edema.