When the chondroitin sulfate chains released by alkaline borohydride treatment were analyzed by digestion with chondroitinase AC-II, chondroitinase ABC, chondro-6-sulfatase and chondro-4-sulfatase, the results showed that all the samples contained glucuronosyl-N-acetylgalactosamine (chondroitinase AC-II-susceptible sequences, 72-86%) and iduronosyl-N-acetylgalactosamine (chondroitinase ABC-susceptible sequences, 14-28%), containing 4-sulfated N-acetylgalactosamine (50-70%) and 4,6-disulfated N-acetylgalactosamine (30-50%).