Summary:The history of chymopapain chemonucleolysis (CNL) has been peppered with controversy since CNL was first used 30 years ago for the treatment of unremitting sciatica of a herniated nucleus pulposus. Numerous studies from the United States, Europe, Canada, and Australia have shown that the procedure is a safe, effective, and practical alternative to laminectomy at an average of approximately half the cost of surgical diskectomy. Neurological complications have been shown to be due to faulty surgical technique, and anaphylaxis can be avoided in >99% of patients by using sensitivity testing. Through careful management, no deaths have occurred from anaphylaxis since 1987. Patient selection criteria for CNL are more rigorous than for laminectomy and must be carefully followed for a successful outcome. Long-term outcomes of CNL patients indicate that good to excellent results are enduring and compare favorably with those of laminectomy. A protocol for investigating chemonucleolysis in cervical disk herniation is being developed; positive results from Europe should pave the way for the expanded use of CNL in the United States. Although studies of other lytic enzymes are being conducted, chymopapain remains the standard by which they are to be judged.