The Cox Tee Dee 0.010 is a two-stroke 0.010 cubic inch model engine designed to power small propeller-based hobby aircraft. First manufactured in 1961, it remains the smallest working piston engine ever mass-produced, but no scientific measurements of its performance are available in the open literature. These measurements are important because they could facilitate the development of small unmanned air vehicles. This thesis reports measurements of power output and efficiency using a specialized dynamometer. An unsuccessful attempt is made to correlate the measurements with simulations based on Stanford University's Engine Simulation Program (ESP). Instead, the results are compared to the predictions of a simple zero-dimensional thermodynamic MATLAB simulation of an engine cycle developed at the University of Maryland. Differences and correlations are discussed and the engine performance is analyzed in the context of propulsion systems for small UAVs and for compact power generation.