Fifty percents of patient with achondroplasia present neurological disturbances of varying degree. Congenital narrowing of the spinal canal in achondroplastics seems to be the main cause of the cord disturbance, and there are several other causes such as prolapse of intervertebral discs, spondyloarthitic degenerative manifestations and wedging of vertebral body. Surgical treatment of the cord disturbance consist of anterior decompression with fusion and posterior decompression. We experienced L1-2 disc herniation in achondroplasia with rapid progression of neurologic symptoms and treated with posterior decompression. Two years after operation, the patient had good result.