This study investigates the relation of total quality management (TQM) and just-in-time purchasing (JITP) with respect to firms' performance, based on theories from operations management, organization theory, strategic management and marketing. U.S. companies have implemented TQM and JITP techniques to improve their global competitive position. The lack of empirical research on how these techniques effect firms performance makes it necessary to explain their strategic values as management invations. In this study, a cross-sectional mail survey was used with the target population of firms in the continental United States that have implemented either technique, or both. The results indicate that the extent of TQM and JITP implementation positively correlates with a firm's performance. Furthermore, the relation between JITP and financial and market performance is more significant in those industries that face high as opposed to low foreign competition. In this study, the validity of findings was assessed in four parts: statistical conclusion, internal, construct, and external validity. Each validity type is defined and its threats are discussed. Based on the findings, a revised research model is offered. The author also tes likely avenues of future research for theorists and practitioners.