Two complete system architectures for a guidance, navigation, and control solution of small UAVs are presented. These systems (developed at the University of California Santa Cruz and the University of Minnesota) are easily reconfigurable and are intended to support test beds used in navigation, guidance, and control research. The systems described both integrate a low-cost inertial measurement unit, a GPS receiver, and a triad of magnetometers to generate a navigation solution (position, velocity, and attitude estimation) which, in turn, is used in the guidance and control algorithms. The navigation solution described is a 15-state extendedKalman filter which integrates the inertial sensor and GPSmeasurement to generate a high-bandwidth estimate of a UAV’s state. Guidance algorithms for generating a flight trajectory based on waypoint definitions are also described. A PID controllerwhich uses the navigation filter estimate and guidance algorithm to track a flight trajectory is detailed. The full system architecture – the hardware, software, and algorithms – is included for completeness. Hardware in the loop simulation and flight test results documenting the performance of these two systems is given.