Glycosaminoglycans (GAGs) are important constituents of the extracellular matrix that make significant contributions to biological processes and have been implicated in a wide variety of diseases. GAG-degrading enzymes with different activities have been found in various animals and microorganisms, and they play an irreplaceable role in the structure and function studies of GAGs. As two kind of important GAG-degrading enzymes, hyaluronidase (HAase) and chondroitinase (CSase) have been widely studied and increasing evidence has shown that, in most cases, their substrate specificities overlap and thus the "HAase" or "CSase" terms may be improper or even misnomers. Different from previous reviews, this article combines HAase and CSase together to discuss the traditional classification, substrate specificity, degradation pattern, new resources and naming of these enzymes.