Contents and structural characteristics of hioactivity polysaccharides such as polyuronans, fucoidans and laminarans were studied for five species of brown seaweed, S. swartzii. S. olygocystum, S. polycystum, Pildina australis and Turbina ornata, widespread in Nhatrang Coast. The yield of laminarans of studied seaweeds was insignificant (no more than 0,8 percent). Laminaran was absent. in Turbina ornata. On the basis of 13C NMP spectnlm laminarans were 1,3
1,6-beta-D-glucans. The yield of fucoidans was from 0,89 (Turbina ornata) before 2,8 percent (S. oligocystum). All fucoidans were sulphated galactofucans. The main components were fucose and galactose:along small amounts of xylose and mannose. All studied species of seaweeds were also rich for alginic acids. It were contained from 11,10 percent (S. polycystum) to 13.83 percent (Turbina ornata).