Fracture of the posterior margin of ring apophysis in lumbar area has been reported as the fracture of posterior margin of body, separation of the posterior rim, rupture of the lumbar cartilage plate into spinal canal or lumbar posteror marginal inter-osseous cartilagenous node. It was regarded as a rare lesion, because of the difficulty in exact detection by conventional radiographic method. Recently, as computed tomography enables to find the detailed configuration, the numbers of reported cases were increased. The lesion occurs in adolescent period by the strenuous sports activity causing flexion of lumbar spine. The authors report the three cases which had been surgically treated and followed more than two years. Symptoms were developed after jumping in two and after falling down from two meters height in one during adolescent period. All three showed severe radiating pain, neurological claudication, and restriction of lumbar motion, before operation. Computerized tomography revealed marked central stenosis due to the protrusion of osseous posterior rim of body into the spinal canal. Dural sac and the roots were decompressed by anterior excision of protruded osseous portion and disc materials. Back pain and the neurological signs showed excellent improvement, and the straight leg raising test was normalized in all cases. It was concluded that the lesion should be distinguished from the simple disc herniation and be treated by appropriate methods.