This paper presents an Agent-based Process Management System (APMS) architecture that combines recent developments in autonomous agent technology and distributed computing platforms. It argues that a service-oriented view is required in order to meet the requirements of open distributed enterprises, now and in the future. This approach embraces and fully supports the decentralisation of responsibility and local autonomy, within and across enterprises. The paper begins by summarising existing approaches to workflow. It describes the APMS approach which extends workflow with the abilities to anticipate process requirements, to resource processes dynamically, and to adapt to exceptions. An important feature of APMS is the absence of a centralised business process representation. Finally, the paper describes an implementation of the APMS architecture, and discusses the engineering issues related to realising such a system within a large organisation.