In this article we propose a new complementary approach to investigate Inter-Organizational Information Systems (IOIS) adoption called configuration analysis. We motivate the need for a new approach by the common observation that the structure and the strategy of an IOIS are interdependent and that the IOIS adoptions consequently cluster orderly. For example, an IOIS setup with a powerful customer as a hub and many suppliers as spokes frequently surfaces across diffusion studies. Yet, this fact has not been integrated into existing analyses, and its implications have not been fully developed. We propose that IOIS scholars need to look beyond the single adopting organization in IOIS adoption studies and in contrast consider adoption units what we call an adoption configuration. Each such configuration can be further characterized along the following dimensions: (1) vision, (2) key functionality, (3) mode of interaction, (4) structure and (5) mode of appropriation. In addition, these dimensions do not co-vary independently. For example, a particular organizing vision assumes a specific inter-organizational structure. A typology of IOIS configurations for adoption analysis is laid out consisting of dyadic, hub and spoke, industry and community configurations. Specific forms or adoption analysis are suggested for each type of configuration. Overall, configuration analysis redirects IOIS adoption studies both at the theoretical and the methodological level, and a corresponding research agenda is sketched.