Most thoracic surgery studies indicate that hospital and surgeon procedure volume are inversely associated with mortality. However, controversy exists regarding the strength and validity of this volume-outcome association. Because thresholds of procedure volume are used to recommend the regionalization of care, investigation of the volume-outcome relationship is imperative. This article examines the methodology used in the volume-outcome relationship literature and highlights important areas of concern. Careful examination of the literature demonstrates that lung and esophageal cancer resection volume is not strongly associated with mortality and should not be used as a proxy measure for quality.