Abstract: The invention pertains to a mucopolysaccharide fraction obtainable from heparin or from fractions including heparinic constituents of molecular weights from 2,000 to 50,000, which has a Yin-Wessler titer which is high relative to the USP titer. It contains components whose molecular weights are less than 10,000, particularly oligosaccharides in the area of 2,000-3,000, comprising from 8 to 12, notably 10 monosaccharide units, among which glucosamine units whose primary positions are sulphated. The last mentioned oligosaccharides include one N-acetyl-glucosamine unit per two units of 2-0-sulphate iduronic acid and per two N-sulphate-glucosamine units, the other saccharide units being of a different nature and including distinct substituents.