391 patients with moderate degenerative lumbar spinal stenosis and intermittent neurogenic claudication were included in this randomized controlled trial. The purpose of this study was to compare the 3-year clinical outcomes of the Superion® InterSpinous Spacer to the X-STOP® device for treatment of moderate lumbar spinal stenosis. Significantly more patients in the Superion® group achieved the predefined FDA composite clinical success endpoint and had a clinically significant improvement to VAS leg pain at 3 years compared to the X-STOP® group. The proportion of patients with clinically important improvement in VAS back pain, ODI disability score, and ZCQ scores for physical function, symptom severity, and satisfaction were all statistically similar between groups.