This study considers work relationships as social exchange relationships in small and mid-size enterprises (SMEs). It focuses on, in addition to economic determinants of exchange, the preconditions for and mechanisms facilitating the development of social reciprocity. Especially in SMEs, the integration of employees and the coordination of work tasks are determined by collectively developed and shared social rules and norms. The perception of the enterprise as a "collective project" represents an important success factor for internal cooperation.