Fifty-five adolescents between the ages of thirteen and nineteen years underwent chemonucleolysis for one or more herniated lumbar discs at St. Michael's Hospital, Toronto, Ontario. The surgery was done by the senior one of us (J.M.) between 1972 and 1982. The duration of symptoms ranged from two months to three years. Pain in the lower limb was the predominant symptom in forty-eight patients. Reduction of the amount of straight leg-raising by 50 per cent or more, with or without pain in the ipsilateral hip when the asymptomatic limb was lifted (cross-over pain) and with or without pain radiating up or down the lower limb when the tibial nerve was pressed in the popliteal fossa (bowstring discomfort), was considered evidence of tension on or irritation of the nerve root and was present in all patients. Chemonucleolysis was considered as an alternative to discectomy and was performed only after the patient failed to respond to conservative management. An anaphylactic reaction occurred in one patient and was treated successfully. The most common symptom after injection was increased back pain, and it was controlled with medication. One patient had transient weakness of the extensor hallucis longus after injection. The length of follow-up ranged from two to twelve years (average, four years and six months), excluding one patient who was killed in an accident six months after injection. Chemonucleolysis did not relieve the symptoms in eleven of the fifty-five patients. These eleven patients all subsequently had surgical excision of the disc, and in them the chemonucleolysis was considered to have failed.(ABSTRACT TRUNCATED AT 250 WORDS)