A two-sided piezoelectric traveling-wave rotary ultrasonic motor is being developed for a high-torque, low-speed application. In the symmetric two-sided configuration, the elliptical motion of teeth on both sides of the vibrating element is coupled to two respective interfaces, inherently increasing the motor's torque capability at reduced rotating speeds. Greater torque densities are attainable than with present configurations which operate with a single interface, enabling reduced size and mass and expanding the potential for direct-drive applications. The design of a two-sided motor prototype was initiated with a previously developed nonlinear physical dynamics model for the purpose of predicting, a priori, steady-state motor performance in a timely, automated manner. To assess the model's merit, the performance of a similar commercially available one-sided motor was simulated and compared to experimentally obtained measurements. Then, using the knowledge gained from correlating the two, a two- sided motor was designed to output significantly greater torque. A prototype was realized, and its speed-torque and efficiency-torque characteristics were obtained and compared to the predicted curves. Impressive stall torque and torque density have been achieved, yet lower than expected performance raises questions regarding the contact profile. Careful redesign of the passive interface washers to improve performance constitutes ongoing work, and improvements to the model are suggested which would alleviate present limitations and make it a more powerful design tool.