The authors report radiological findings in 13 cases of avulsion of the posterior lumbar apophyseal ring. The lesion affected young adults in 10 cases and adolescents in 3 cases. The lesion involved the inferior endplate of L4 in 11, and of L5 in 1 patient, and of L3 in 1 patient. 6 patients presented with unilateral sciatica, 3 with bilateral sciatica, and 4 with low back pain. Acute spinal trauma was evident only in 2 adolescents. Radiological recognition of the lesion was possible on plain films in 9 cases. CT demonstrates association of avulsion of the posterior vertebral apophyseal ring and herniated disc in all cases. Avulsion of the posterior apophyseal ring has to be differentiated from posterior longitudinal ligament, annulus, or herniated disc calcifications, as well as from posterior degenerative ridge osteophytes. Controversy about physiopathology of the lesion remains: weakness of the apophyseal ring during childhood and in patients with Scheuermann's disease may explain avulsion of the apophyseal ring in association with median disc herniation.