The composition of the extracellular polysaccharides of 10 strains ofRhizobium melilotiwas investigated. Glucose, galactose, and glucuronic acid were found as components; their amounts, determined after hydrolysis as a percentage of the total sugars, varied from 82 to 86 for glucose, 13 to 16 for galactose, and 0.4 to 1.2 for glucuronic acid. No significant difference between the strains was found, which suggests a homogeneity of the extracellular polysaccharides ofRhizobium meliloti.