Supply Chain Management, the coordination of upstream and downstream flows of product, services, finances, and information from a source to a customer, has risen in prominence over the past fifteen years. The delivery of a product to the consumer is a complex process requiring action from several independent entities. An individual firm consists of multiple functional departments, each responsible for one aspect of customer service. In the traditional corporate structure of functional silos, there is little communication between Purchasing, Manufacturing, and Logistics, and yet these departments comprise three core supply chain processes of a firm. Ironically, managers report that it is easier for Purchasing to integrate with suppliers and Logistics to integrate with customers than it is for either group to integrate within the firm. This study develops and tests a model of factors that influence the level of internal integration of three key internal supply chain management functions: Purchasing, Operations, and Logistics. These three functions define the internal supply chain because they are responsible for the introduction of raw materials, transformation into product, and movement of the product to the customer. Prior research has established that interdepartmental integration improves performance in various contexts. However, given the vast range of diversity in firms and industry environments, it is unlikely that there is only one way to accomplish interdepartmental integration. The research model is grounded in Organizational Information Processing Theory (OIPT). Conceptually, OIPT posits that the performance of a firm is a function of the fit between the information processing requirements created by the environment and the information processing capabilities created by the organizational design. The purpose of this research is to answer the following research questions. First, what factors influence the level of internal integration within a manufacturing firm? Second, how are these factors interrelated? Third, do the relationships between the factors vary depending on the task environment? The methodology selected was a cross-sectional survey of manufacturers in the United States. Path analysis was used to test the research hypotheses. Results generally support the research model. Several factors included within the research model have significant effects on Collaboration and Strategic Consensus, the outcome variables used as indicators of integration. Hypothesized mediation effects are also supported. Moreover, the level of Uncertainty moderates two of these relationships, supporting the use of the OIPT theoretical lens. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]