In routine views of lumbar spine, posterior arches are hard to evaluate because there are so many lines and overlapped each other. Therefore, recognition of abnormality of posterior arches is difficult, requires painful and scrupulous observation. Author introduce useful signs in delineation of posterior arches of lumbar vertebrae. It might be called“cow head sign”on anterior-posterior view and“pawing dog sign”on lateral view, respectively. In“cow head sign”, superior articular facets correspond to each horns of cow head; pedicles to eyes; trensverse processes to ears; inferior articular facets to mouth; laminae to face and spinous process to nose. In“pawing dog sign”, pedicles correspond to front paws; superior articular facets to neck; laminae to trunk; inferior articular facets to hind paws and spinous process to tail. Author dare to say that if one applys this sign in observing lumbar spine radiographs, he can interprete them more easily and quickly.