Heparin (Hep), hyaluronic acid, chondroitins (sulfate) A, B, and C, and heparins (sulfate) A, B, C, and D were subjected to microelectrophoresis in barbital-agarose gel, fixed with cetylpyridinium chloride and stained with toluidine blue. The optical densities of the resulting bands were compared with optical densities obtained upon reaction with azure A in aqueous solution and with the carbazole reagent. A linear relation was obtained between optical density and concentration of purified sulfated mucopolysaccharide (SMP). Less than 1 microgram of Hep and 2 microgram of other SMPs are required for measurement by electrophoresis, while about 30 microgram of each is required with the carbazole reagent. The optical density of a mixture of SMPs was equal to the sum of the densities for the individual SMPs upon microelectrophoresis. It was demonstrated that the individual SMPs in mixtures were distinguishabed by reaction with specific enzymes and by changes in migration in agarose with barbital, phthalate, ethylenediamine, or propanediamine buffers, permitting ready demonstration and quantitation of various SMP species. Examples are shown of the application of the procedure to measure the total SMPs and individual SMPs in tissue extracts. The method is sensitive, reproducible, flexible, and measures quantities 1/30th of those measured colorimetrically, yet is relatively unaffected by protein, carbohydrate, or inorganic electrolytes.