The glycosaminoglycans of sciatic nerves recovering from crush-injury were studied in adult guinea pigs and compared with those of non-injured mature neural tissues. The glycosaminoglycans were recovered from the 1,900 g supernatant and pellet of the tissue homogenates and assayed for hexuronate contents and susceptibilities to hyaluronidase, chondroitinase ABC, and nitrous acid. In the normal brain and central nerve tracts, the glycosaminoglycans were distributed both in the supernatant and pellet fractions; the brain showed a predominance of chondroitin sulphates but the tracts showed a predominance of heparan sulphates. Twice as much glycosaminoglycans were found in normal sciatic nerves, only in the pellet fraction and with heparan sulphate predominant. In the 2 weeks post-crush, progressive increase in hexuronate was observed, due mainly to additional chondroitin sulphate forms in the supernatant; the pellet fraction in the same period was however similar to the untreated controls in relative abundance of glycosaminoglycan classes and hexuronate content. At 4 weeks post-crush, although the total hexuronate returned to the control level, a significant proportion of glycosaminoglycans remained in the supernatant fraction. Evidence is thus provided for the need to modulate the glycosaminoglycan expression pattern in adult neural tissue to allow post-traumatic tissue remodelling and axonal regrowth.