Stirling cycle engines offer potential advantages over internal combustion engines in fuel choices, noise, and emissions. A free-piston Stirling cycle engine-pump (FPSEP) has been investigated for potential use in human-scale, fractional horsepower applications. A design has been developed in the Fluid Power Research Laboratory at the University of Wisconsin-Madison that combines a free-piston Stirling engine with a singleacting piston pump. The design utilizes a pneumatic cylinder to drive the engine's displacer that in turn, controls engine speed. The performance and dynamic characteristics of this FPSEP have been simulated to predict its operating characteristics over a wide range of conditions. The simulation results indicate that a FPSEP operating at 3.8 MPa (550 psi) working gas pressure and with an engine displacement of 24.8 cm (1.5 in) running at 4400 cycles per minute could produce 1.3 kW (1.8 HP). A proof-of-concept engine-pump has been built and tested to validate the simulation results. In this device, heat is supplied by an electric heater and cooling is provided by water. At this time, the engine-pump has produced a low level of useful power while its operation has been limited to operating at 0.62 MPa (90 psi) working gas pressure while running at 120 cycles per minute. While the performance predicted by the simulation has not yet been achieved, work is continuing on extending the operating envelope for the engine-pump.