Succinoglycans are bacterial exopolysaccharides with an octasaccharide repeating unit, composed of glucose and galactose in a 7:1 molar ratio of, and non-carbohydrate substituents, including pyruvate, succinate and acetate. The succinoglycans produced by four different strains of Sinorhizobium meliloti, gram-negative soil bacteria, were analyzed for their molecular weight distribution and degree of non-carbohydrate substitution, as well as their chemical properties were related to their rheological properties. These results showed that the ratio of high molecular weight to low molecular weight succinoglycan was varied from 0.50 to 2.36. Degree of succinylation among the bacterial strains was in the range of 0.30-1.90. Therefore, we concluded that each strain produced succinoglycans with different average degrees of polymerization and succinylation: and that these characteristics were correlated to the theological properties of the solutions. The effect of molecular weight on the theological properties appeared to be less than that of the succinyl group abundance. Published by Elsevier Ltd.