Polysaccharide isolated from encapsulated Klebsiella pneumoniae, type B, consisted of glucose, glucuronic acid and rhamnose. C14 was incorporated biosynthetically into these 3 components from acetate-1-C14 added to the media. Following injection of the Cl4-labeled polysaccharide into animals, up to 80% of the labeled material was recovered from animal tissue by a combination of enzymatic and extractive procedures. Much of the C14-labeled material in tissue retained its original haptenic properties and relative C14 content of the constituent monosaccharides.