One hundred and twenty consecutive patients who had primary excision of a lumbar disc at a single level for predominantly radicular symptoms were studied. Of these patients, eighty-seven (72 per cent) were available for comprehensive review. The duration of follow-up ranged from twenty-four to eighty-seven months (average, thirty-eight months). Radiculopathy was initially relieved in eighty-six (99 per cent) of the patients, although six patients (7 per cent) had recurrent herniation, which was successfully treated by reoperation. In an additional twelve patients (14 per cent), the operation was deemed a failure due to subsequent disabling low-back pain. Narrowing of the disc space was present radiographically in 98 per cent of the patients, but the amount of narrowing did not correlate with the degree of low-back pain, the age of the patient, or the length of time after operation. Factors predisposing to failure of the operation due to disabling low-back pain included coverage under Workmen's Compensation (p less than 0.00001), a history of more than fifteen pack-years of cigarette-smoking (average, one pack a day for fifteen years) (p less than 0.01), and an age of more than forty years (p less than 0.05).