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The authors prospectively followed the natural evolution of lumbar disc herniation in 48 patients treated by conservative measures. The initial computed tomographic sean was obtained during the acute phase of the disc herniation and the second was performed 1–48 months after healing. The initial computed tomographic scan allowed classification of the herniations according to size: 13 were considered small, 20 medium and 15 large. Comparison with follow-up computed tomographic scans showed that 9 of the herniations decreased by at least 25%, 8 decreased between 50 and 75% and 31 decreased between 75 and 100%. In the later group, a few had disappeared even though the second computed tomographic scan was performed as early as the month immediately after successful treatment. The largest herniations were those which had the greatest tendency to decrease in size. It is postulated that this could be secondary to the herniation breaking through the outer fibers of the anulus and entering the epidural space.