Objective To explore the prevalence of multilevel lumbar spondylolysis in operation patients,and to evaluate the diagnostic value of CT reconstruction on multilevel lumbar spondylolysis.Methods A total of 312 patients,who had undergone surgical treatment in our hospital from January 2004 to March 2012 for lumbar spondylolysis,were enrolled in this study.There were 147 males (47％) and 165 females (53％),aged from 12 to 76 years (average,44 years).Every patient underwent lumbar spine X-ray examination including anteroposterior,lateral,over-flexion,over-extension and double oblique X-rays,as well as CT examination.The prevalence of multilevel lumbar spondylolysis in all operation patients and the involved segments were recorded and analyzed.Moreover,the clinical manifestation and radiological features were summarized.Results In all enrolled patients,there were 9 patients (2.9％) with multilevel lumbar spondylolysis,including 5 males and 4 females,aged from 21 to 51 years (average,39 years).As for lesion distribution,there were 8 cases of bilateral spondylolysis located at both L4 and L5,and 1 case of bilateral spondylolysis at L5 combined with right spondylolysis of L4 and discontinuity in the base of left pedicle of L4.Among 9 patients,only 3 patients obtained correct diagnosis by anteroposterior and double oblique X-rays of the lumbar spine,while all patients got final diagnosis by sagittal and oblique coronal reconstruction of lumbar spine CT scan.The oblique coronal CT reconstruction could show the details of bone defect in lumbar vertebral isthmus,bony callus,peripheral osteophytes,as well as fibroplasia.For unilateral lumbar spondylolysis,the oblique coronal CT reconstruction could also show the reactive sclerosis in contralateral lamina of vertebra.Conclusion Multilevel lumbar spondylolysis is not rare in operation patients,and L4 and L5 are most common involved levels.Sagittal and oblique coronal reconstruction of lumbar spine CT scan is more accurate in showing the details of lumbar spondylolysis,which is helpful in decreasing the missed diagnosis and improving therapy.