Lumbar interbody fusions are being performed with increased frequency in the last decade. Anterior and posterior interbody techniques have demonstrated relatively similar success rates. Nonetheless, despite increased attention to cost-effective care delivery, approach-related differences in procedural cost and predictors for these differences remain poorly defined. The purpose of this investigation was to characterize the variability in cost for anterior versus posterior-based lumbar interbody fusions and to identify key predictors of procedural cost.