Abstract: In a world of electronic interconnectivity, the concepts for process automation within a single organisation need to be extended to support cooperation with customers and partners across organisational boundaries. Current workflow standards bodies provide limited support to enable this interconnectivity. They provide interfaces and data structures for interoperability but they do not address various aspects of the coordination and dynamic composition of processes. We propose a model for tiering business processes into the private business processes of organisations, and those shared business processes that interconnect them. Private business processes can expose interaction points, and shared processes can link to these points so that an overall business process may span two or more organisations. The interaction points can selectively expose information about the processes and process tasks of an organisation. The paper also presents how these modelling ideas can be supported by a coordinating architecture and describes a prototype that implements the key ideas. The proposed architecture that supports inter-organisational business processes was initially validated in the Vega [7], [8], [9] final demonstration [11, Chapter7] that brought together six different companies in a virtual enterprise. The implementation built upon OMG's Workflow Management Facility Specification concept [3] [4] for inter-workflow management interfaces, incorporated existing workflow management systems, including SAP R/3, and also non process-oriented systems. Available services were selected at runtime according to their capabilities and their availability. Experience from the demonstration with all the involved components showed a dynamic linkage between existing business processes, and reliable communication between the business partners.