BACKGROUND Tandem spinal stenosis (TSS) is defined as spinal stenosis that combines cervical and lumbar spinal stenosis. The primary manifestations include intermittent neurological claudication, progressive gait disturbance, and mixed symptoms and signs of the upper and lower extremities. METHODS From April 1994 through September 1995 in a series of 158 patients who underwent surgery for spinal stenotic syndrome, 12 patients were diagnosed with TSS, with an overall incidence of 7.6%. Our management guidelines required that cervical surgery be performed first if the patients had signs in the upper motor neuron region or predominant signs in the upper extremities. In the patients who had significant symptoms in the lower extremities and no signs in the upper motor neuron region, lumbar surgery was performed first. RESULTS In this series, 8 of 12 patients received cervical surgery first and 4 required further lumbar surgery. Among the 8 patients who received cervical surgery, 2 received Hirabayashi's laminoplasty, 3 laminectomy, and 3 anterior decompression and fusions. The other 4 patients received lumbar surgery only. The average follow-up period was 32 months (range, 24-40 months). At the latest examinations, 8 patients (66.7%) had excellent or good clinical results. CONCLUSIONS Our results revealed that when correct diagnosis and management for patients with TSS was given, the patients usually had satisfactory outcomes. Ossification of the posterior longitudinal ligament (OPLL) was noted in 7 of 12 patients (58.3%) in this study. Thus, OPLL might be a predominant factor in TSS, and larger populations studies are needed to confirm this finding.