The intracytoplasmic accumulation of polysaccharides has been demonstrated in four species of Streptomyces. After extraction and purification, the structural properties of these polysaccharides were investigated by chemical, spectrophotometric, and enzymatic methods. The results clearly indicated that the streptomycete polysaccharides have a degree of branching and a macromolecular structure similar to that of the glycogens isolated from other bacteria and animal sources.