The studies of the occurrence and changes of experimental brain edema have been observed by calculating wet weight, volume, dry weight, per cent water content and swelling per cent in 12 normal rabbits as a control group and 24 rabbits of experimental group. The brain edema was induced by expansion of laminaria which resulted in brain compression, that was inserted into the supratentorial extradural space of rabbit. The piece of section of laminaria which is a sea weed and used for the purpose of slow expanding space-occupyin gmass has a characteristic mode of slow expansion in volume on contact with water. The average wet weight of cerebral hemisphere of normal rabbits was 3.30+/-0.19 gm. The average dry weight of unilateral hemisphere of 156 from 78 rabbits was 0.69+/-0.04 gm, while its volume was 2.97+/-0.29 ml and the percentages of water content was 78.92+/-1.36 per cent. The weight, volume and percentages of water content and swelling in the compressed sides of hemisphere showed higher values compared them to the opposite noncompressed hemisphere in the "laminaria-compression" group and showed gradually increasing tendency in the values as the time elapsed.