The dermatan sulfates from hog, rat, rabbit, and beef liver, hog, rat, beef, and dog spleen, and hog skin were isolated and submitted to structural analysis. All of them migrated as single bands, close to the standard position for dermatan sulfate in agarose-gel electrophoresis. In polyacrylamide gel, however, each dermatan sulfate showed a characteristic electrophoretic migration-pattern: one, two, or three polydisperse bands, corresponding to different molecular weights, were obtained for the dermatan sulfates according to their origins. Chemical analysis showed that all of the dermatan sulfates here described are hybrid polymers composed of D-glucuronic and L-iduronic acid-containing disaccharide units. The relative position of these units in the polymer chains and the presence of 6-sulfated disaccharides were determined with the aid of chondroitinases B and AC from Flavobacterium heparinum. These studies show that each dermatan sulfate has a unique structure as regards the molecular weight, the presence of 6-sulfated disaccharide units, and also the relative amount and position of glucuronic and iduronic acid residues in the chains. These findings suggests a tissue- and species-specificity for the dermatan sulfates.