During the twelve-year period from January 1, 1970, through December 31, 1981, 4,282 patients with the diagnosis of herniated nucleus pulposus were treated by intradiscal injection of chymopapain under local anesthesia. Fifteen (0.35 per cent) of these patients sustained an anaphylactic reaction as defined by us. Twelve patients had subjective early warning signs before their blood pressure decreased, including a total-body burning or tingling sensation (five patients), a general feeling of ill health (four patients), and diffuse pruritus (three patients). Profound hypotension without subjective warning symptoms was the first indication of anaphylaxis in three patients. In all patients, hypotension requiring vigorous treatment was the life-threatening clinical manifestation of anaphylaxis, but respiratory distress severe enough to require endotracheal intubation did not occur. There were no deaths or known sequelae. Ten of the fifteen patients were women. Review of the medical histories of the fifteen patients and follow-up telephone interviews did not identify any other pre-disposing factor for the anaphylaxis. Twelve of the fifteen patients obtained complete relief of the symptoms of disc herniation. The advantage of the use of local rather than general anesthesia for chymopapain injection is that the patient remains responsive and can give an early warning of the subjective symptoms of anaphylaxis if they appear. This potential for early diagnosis allows early and aggressive treatment with intravenous fluids, epinephrine, steroids, and antihistamines, which can be effective in preventing death or permanent sequelae. In our experience, general anesthesia and routine endotracheal intubation are not necessary for intradiscal injection of chymopapain.