Controversy exists about the lumbosacral transitional vertebrae(LSTV) causing low back pain and lumbar disk abnormalities such as herniated nucleus pulposus(HNP), early disk degeneration or annulus bulging. the prevalence of the lumbosacral transitional vertebrae were evaluated. The classification of LSTV is presented based upon the radiomorphological changes of transverse process of the last presacral vertebra. The type Iis dysplastic transverse process, typeII is incomplete lumbarization/sacralization, type III is complete lumbarization/sacralization, and type IVis mixed(typeII and type III). Simple radiographic findings of (804 patients including) 300 patients without low back pain, 400 patients with low back pain and 104 patients with disk abnormalities on CT scan have been analyzed. The prevalence of LSTV were 51.5% in normal control group, 40.8% in low back pain group and 46.2% in disk abnormality group. The type Iis regarded as the forerunner of a true transitional vert bra and the prevalence of the true LSTB (typeII, III, IV) were 11.6%, 18.3% and 13.5% on each groups. The typeII&III in low back pain group and type IIin disk abnormality group were relatively increased in incidence of LSTV than in normal control group. A patient with the type IIorIIIof the LSTV may show low back pain more frequently than a patient without such a LSTV. The typeIIof LSTV may cause lumbar disk abnormalities more frequently.