Chymopapain and collagenase are well known chemonucleolytic agents for lumbar disc herniation. However, these enzymes have serious problems occasionally, such as severe neurotoxicity or anaphylaxis even fatal to patients. Chondroitinase ABC, a metabolic product of Proteus vulgaris, has a specific action on the proteoglycans of the nucleus pulposus, but rarely no effect on the intrathecal nerve tissues of vessels. Seventy eight rabbit lumbar discs were evaluated radiographically and histologically after injection of chondroitinase ABC 40U/ml per disc and compared with buffer injected group and nonigected control group. There was considerable disc space narrowing of the chondroitinase ABC injected group which was verified radiographically and histologically(p<0.01). A zone of Safranin 0 depletion was present in the ventral anulus fibrosus adjacent to the nucleus pulposus in all treated discs, indicating proteoglycan loss. On electron microscopic findings there were collapse of chondrocytes and notochordal cells. All of these findings are corresponding to the evidence that chondroitinase ABC may be another chemonucleolytic agent by decreasing disc volume and thereby decompressing spinal cord or nerve roots. All histologic effects of chondroitinase ABC were confined to intervertebral disc tissues. Chondroitinase ABC deserves to be a study object for the alternative of chemonucleolysis.