With increasing maturity of the enterprise stable basic conditions and co-operations in and between enterprises win at meaning. Big synergies are to expect in the co-operation of middle-sized enterprises. Developments in the motor-industry show ways for suppliers to work together as System-Suppliers or Virtual Organizations. Results of two Research projects deliver proven ways for implementing such co-operations with medium-sized enterprises: Quality beneficial customer-supplier-relations: In this already finished combine project suppliers of various Production-levels formed solutions for their customers ill common. Common execution of development-projects with co,competitors: Direct competitors show ways to develop innovative branch-standards together. Base of a successful co-operation forms the enterprise-internal ability to work together in teams e.g.. It is coined by the persons involved. Attempts of Total Quality Management (TQM) promote the co-operation ability of the employees by internal customer-supplier-relations and crossfunctional process-management. The internal experiences can be transferred to the enterprise co-operation. Organizational concepts are implemented in common by the enterprises. The attempts of organizational planning and organizational development have to be considered by doing this. The cooperation lay-out is performed in two steps: The initiation of the cooperation is determined by the active work of the top-management based on a consens about the objectives. In the project-work reliable basic conditions will at meaning for the engaged employees based on their competences. A generalized concept for implementing co-operations will be demonstrated by instances of the Research projects.