This paper explores the diffusion of Electronic Data Interchange in Denmark. EDI forms a complex and interorganizational innovation and therefore a multitheoretical framework is suggested to study its diffusion. The framework takes into account institutional, industry specific and organizational factors and thus extends the analysis beyond organizational borders. The framework delivers an account of EDI diffusion in Denmark based on field study data. The field study covers three industries in Denmark; the finance, the retail and the transportation sector. The study clarifies how organizational, industry and environmental factors simultaneous are brought to bear to understand the diffusion process. The content analysis distinguishes six diffusion patterns and associated mechanisms that mold diffusion patterns in three diffusion arenas: local dyadic relationships, industry networks, and national initiatives. The analysis demonstrates that EDI diffusion is a complex interplay of organizational, industry and institutional factors. On the theory plane the study calls for the need to orchestrate multitheoretical approaches to study the diffusion of complex, and networked technologies.