The purpose of this research was to study customer-supplier relationships, and particularly their partnerships, to help managers and practitioners successfully design, develop, implement and deploy tools and joint practices for their upstream systems. To achieve this purpose, a total of 1,811 (potential mailed survey questionnaire respondents) and 7 (structured interviewees) managers who are responsible for purchasing, sales/ marketing, quality-related, and production- or operations-related functions of U.S. private manufacturing companies in SIC 35, 36, and 37 were used to collect qualitative and quantitative data. Using 172 usable mailed survey questionnaire responses (response rate: 9.78%) and qualitative data from the structured interviews, the following major findings were derived: • Four tools/joint practices most frequently used in customer-supplier relationships were supplier certification/verification, joint problem-solving teams, quality audits, and Just-In-Time production and delivery, • Five tools/joint practices that have been used most effectively were ISO 9000 and/or QS 9000 and/or Baldrige criteria, quality audit, JIT production/delivery, joint planning, and joint problem-solving teams, • Five tools/joint practices that have been most internalized were ISO 9000 and/or QS 9000 and/or Baldrige criteria, quality audit, JIT production/delivery, joint problem-solving teams, and supplier or customer performance measurement systems, • Overall perceived organizational performance improvement was 25% (30% quality improvement, 21% cost reduction, and 26% cycle time reduction). In addition to these findings, eight hypothesized relationships were tested using two independent variables (joint use of specific tools and joint use of practices) and four dependent variables (informed partners, role integrity, conflict resolution, and mutuality). The results showed that customer and supplier companies do not share the same experience with respect to the relationships between the two independent variables and conflict resolution. Using these findings, a set of practices was proposed as a means for further improving specific organizational performance dimensions and providing a mechanism to better share the consequences of joint action. / Ph. D.