Nineteen adolescent patients who presented with mechanical-type back pain and vertebral changes consisting of intravertebral disc herniation, disc space narrowing, and minimal wedge deformity are described. The symptoms and signs were primarily located at the dorsolumbar junction. A specific strenuous activity or traumatic event was clearly associated with the onset of symptoms in 16 of the 19 patients. Spondylolysis or spondylolisthesis (grade I or II) at L5-S1 was also found in 32% of the patients. Most patients responded well to a program of rest, exercises, salicylates, and temporary avoidance of the particular activity involved. Some required orthoses to obtain relief. No patient had a progressive kyphotic deformity during the follow-up period. The relationship of this condition to increased stresses applied to the immature spine, particularly in a preflexed posture, is emphasized.