Pseudarthrosis is the result of failed attempted spinal fusion. This condition typically manifests with axial or radicular pain months to years after the index operation. Diagnosis is based on clinical presentation and imaging studies, after other causes of persistent pain are ruled out. The degree of motion seen on flexion-extension radiographs that is indicative of solid or failed fusion remains a point of controversy. Thin-cut CT scans may be more reliable than radiographs in demonstrating fusion. Metabolic factors, patient factors, use and choice of instrumentation, fusion material, and surgical technique have all been shown to influence the rate of successful fusion. Treatment of the patient with symptomatic pseudarthrosis involves a second attempt at fusion and may require an approach different from that of the index surgery as well as the use of additional instrumentation, bone graft, and osteobiologic agents.