Concordia: An infrastructure for collaborating mobile agents. Use of the Internet and the World-Wide-Web has become widespread in recent years and mobile agent technology has proliferated at an equally rapid rate. In this paper, we introduce the Concordia infrastructure for the development and management of network-efficient mobile agent applications for accessing information anytime, anywhere, and on any device. Concordia has been implemented in the Java language to ensure platform independence among agent applications. The design goals of Concordia have focused on providing complete coverage of flexible agent mobility, support for agent collaboration, agent persistence, reliable agent transmission, and agent security. Concordia offers a flexible scheme for dynamic invocation of arbitrary method entry points within a common agent application and extends the notion of simple agent interaction with support for agent collaboration, which allows agents to interact, modify external states (e.g., a database), as well as internal agent states. Concordia provides support for agent persistence and recovery and guarantees the transmission of agents across a network. Concordia has also been designed to provide for fairly complete security coverage from the outset. An alpha release of Concordia is available.