This report summarizes work by the MLB Company (industry partner) and the Research and Engineering Center for Unmanned Vehicles at the University of Colorado at Boulder (CU) (research institution partner) on the cooperative tracking of moving targets by teams of autonomous unmanned air vehicles. This work was performed between September 2004 and July 2005. The following future scenario provides the motivation for this work: A ground vehicle moves at high speed along a mountain road, away from a town where it committed a hit- and-run attack on a group of civilians. The US military forces want to find the attackers and follow them to their hideout. Multiple unmanned aerial vehicles (UAVs) are sent to the area where the attackers were reported to have retreated. One of the UAVs identifies the attackers' vehicle based on reports from the civilians and notifies nearby UAVs of its location. The UAVs alter their flight paths relative to that point, with some moving ahead of the vehicle and others maintaining position near it - without attracting attention from the attackers. As the attackers move through the region, responsibility for direct sensing passes from one UAV to another to always keep the target in sight. Through collaboration, autonomous unmanned air vehicles were able to complete tasks that each could not have done alone.