Chondroitin 4-sulfate and chondroitin were digested with lysosomes under acidic conditions. The contributions of hyaluronidase [EC 3.2.1.35], .beta.-glucuronidase [EC 3.2.1.31], .beta.-N-acetylhexosaminidase [EC 3.2.1.52] and sulfatase [EC 3.1.6.4] to the degradation of chondroitin 4-sulfate were examined on the basis of characterization and identification of the digestion products. Chondroitin 4-sulfate was 1st degraded only by hyaluronidase, and sulfatase did not significantly contribute to the initial degradation of polymeric chondroitin 4-sulfate. In further degradation, the main oligosaccharides produced were normally sulfated odd-numbered oligosaccharides such as tri-, penta-, hepta- and nonasaccharides. Octa- and decasaccharides of chondroitin 4-sulfate were not digested by hyaluronidase, but by the concerted action of exoglycosidases and sulfatase. The dodecasaccharide derived from chondroitin 4-sulfate serves as the lowest MW substrate for hyaluronidase and the decasaccharide as the largest size substrate for .beta.-glucuronidase in the degradation of chondroitin 4-sulfate by the enzymes of lysosomes. The degradation of chondroitin by the lysosomes occurred in a similar way. The difference in the pathways of degradation between hyaluronic acid and chondroitin 4-sulfate may be attributed to their hexosamine compositions. .beta.-Glucuronidase cleaves glucuronic acid in the terminal nonreducing position of even-numbered oligosaccharides which are derived from chondroitin 4-sulfate regardless of the presence of the sulfate residue on the adjacent N-acetylgalactosamine. The sulfated odd-numbered oligosaccharides were resistant to .beta.-N-acetylhexosaminidase. The affinity of .beta.-N-acetylhexosaminidase for the odd-numbered oligosaccharides from chondroitin was lower than that of .beta.-glucuronidase for the even-numbered oligosaccharides. No contribution of sulfatase, which cleaves the sulfate residue of N-acetylgalactosamine at the nonreducing end, was found.