Electronic data exchange along the supply chain has been discussed in the information systems (IS) academic literature for many years and remains a practical problem for enterprises worldwide. In this paper we present a Maturity Model for B2B Integration (BIMM). The model is a result of a longitudinal research project on B2B integration. The BIMM was developed to assess the capability level for electronic document exchange of players in a supply chain and addresses current limitations of existing maturity models. The BIMM was developed a-priori from an extensive literature review and an explorative study of 112 company cases. In the next stage of the research the model will be validated using real-world data from leading B2B integration providers.