Physiological conditions enhancing rhamnose-containing polysaccharide synthesis by Klebsiella I-714 were studied in batch culture (0.3-1 and 2-1 bioreactors). The four carbon sources tested, sucrose, sorbitol, Neosorb and Cerelose, allowed exopolysaccharide production. Larger amounts of polymer were produced when high carbon/nitrogen ratios and complex nitrogen sources were used. Exopolysaccharide synthesis was greatest at 30 °C, which was a suboptimal growth temperature. A reduction in the phosphate content of the medium enhanced rhamnose-containing polysaccharide production. When the initial carbon source concentration was augmented, byproducts other than exopolysaccharide were formed. Rhamnose-containing polysaccharide theology can be modulated by changing the phosphate content of the medium.