Virtual enterprises (VEs) enable the deployment of distributed business processes among different partners in order to shorten development and manufacturing cycles, reduce time to market and operational costs, increase customer satisfaction, and operate on global scale and reach. Dynamic virtual enterprises are an emerging category of VE where the different partners are being selected dynamically during business process execution based on market-driven criteria and negotiation. In this chapter, we present an agent-based platform for the management of dynamic VEs. The main contributions of this approach are the distributed, autonomous agent-based business process management, the XML-based business process definition language, the flexible ontologies, and the dynamic negotiation and selection of partners based on virtual marketplaces. The presented platform has been fully developed using emerging agent and Internet standards like FIPA, MASIF, and XML.