Lumbar spondylolysis generally occurs in adolescent athletes. Bony union can be expected with conservative treatment, however, the fracture does not heal in some cases. When the fracture becomes a pseudoarthrosis, spondylolysis patients have the potential to develop isthmic spondylolisthesis. A cross-sectional study was performed to determine the incidence of spondylolysis and spondylolisthesis, and to elucidate when and how often spondylolisthesis occurs in patients with or without spondylolysis. patients undergoing computed tomography (ct) scans of abdominal or lumbar regions for reasons other than low back pain were included (n = 580). Reconstruction CT images were obtained, and the prevalence of spondylolysis and spondylolisthesis were evaluated. Of the 580 patients, 37 patients (6.4%) had spondylolysis. Of these 37 patients, 19 patients (51.4%) showed spondylolisthesis, whereas only 7.4% of non-spondylolysis patients showed spondylolisthesis (p < 0.05). When excluding unilateral spondylolysis, 90% (18/20) of spondylolysis patients aged ≥60 years-old showed spondylolisthesis. None of the patients with isthmic spondylolisthesis had received fusion surgery, suggesting that most of these patients didn't have a severe disability requiring surgical treatment. our results showed that the majority of bilateral spondylolysis patients aged ≥60 years-old show spondylolisthesis, and suggest that spondylolisthesis occurs very frequently and may develop at a younger age when spondylolysis exists.Lumbar spondylolysis, which is considered a stress fracture of the pars interarticularis, commonly occurs in adolescent patients 1 . In adolescent patients with acute lumbar spondylolysis, bony union can be expected with adequate conservative treatment, such as wearing a brace and refraining from sports activity 2,3 ; however, in some cases, the fracture does not heal and it becomes a pseudoarthrosis.At this moment, there is little information about the long-term prognosis of lumbar spondylolysis in cases where the defect becomes a pseudoarthrosis. Thus, patients may have justified anxiety whether they develop severe lumbar degenerative disease. To clarify the actual long-term prognosis of spondylolysis, a prospective study should be performed. However, because spondylolysis patients are usually adolescent, it is not easy to perform a prospective study requiring over fifty or sixty-year follow-up. We propose that patients need information about the future possibility of lumbar degenerative disease because of the presence of spondylolysis suggested by retrospective or cross-sectional studies.The purpose of the present study is to clarify the future possibility of lumbar spondylolisthesis in patients with lumbar spondylolysis. Although previous studies demonstrated that spondylolysis patients have higher future incidences of disc degeneration and spondylolisthesis 4-7 , there is no detailed information regarding when and how often spondylolisthesis occurs in patients with or without spondylolysis. Therefore, we examined the age-spec...