Extracellular polysaccharides have been isolated from cultures of freshwater and marine bacteria originally isolated from material adhering to surfaces and underivatized hydrolysates have been analyzed by high-performance liquid chromatography methods. A scheme has been developed whereby the uronic acids can be identified on strong anion-exchange columns, while neutral monosaccharides can be separated and identified using aminobonded columns or cation-exchange adsorbent loaded with a heavy metal ion. The methods permit rapid and accurate comparison of polysaccharides with differing chemotype. The strains studied show a range of different chemotypes, all containing a uronic acid and several neutral monosaccharides. Some of the polysaccharides isolated from marine bacteria possessed a very high acetyl content.