The presence of D-glucuronic acid in dermatan sulfate preparations has previously been reported from several laboratories. It has not been clear whether the D-glucuronic acid represents a contamination with another polymer or whether it is actually part of the dermatan sulfate molecule. The present studies were undertaken in order to evaluate this problem more definitively. It is demonstrated that highly purified dermatan sulfate is partially degraded by testicular hyaluronidase yielding polysaccharide fragments with D-glucuronic acid in the newly formed nonreducing termini. The conclusion is therefore reached that D-&Icuronic acid is an integral part of the dermatan sulfate molecule. As a result of the presence of hyaluronidase-susceptible linkages to D-ghCUrOUiC acid residues in the close vicinity of the polysaccharide-bound peptide, a large proportion of the polysaccharide fragments reisolated after enzyme treatment are devoid of amino acids.