Although Extracorporeal Shock Wave Lithotripsy has become the preferred treatment modality for symptomatic renal calculi, there is still no straightforward way for operators to perform quality assurance tests across all devices. The goal of this project is to develop a Stone Phantom Device to determine the number of shock waves necessary to comminute a phantom stone target, thereby testing the lithotripter's shock wave generating, focussing, and stone localizing subsystems, and also the operator's alignment skills. Phase I research successfully demonstrated the feasibility of the approach, with the development of a high resolution weight sensor, a phantom stone with controllable properties in an acoustically transparent mesh holder, and a reliable shock wave detector. The Phase II portion of the project will focus on: l) improving the durability of the stone weight sensor; 2) formulating stone mimicking materials with better long-term immersion stability; 3) refining the stone constraint method to reduce costs; and 4) integrating the system into a complete stand-alone, microprocessor-based prototype for clinical testing. When fully commercialized (with Phase III commitments), the system will used for clinical quality assurance, operator training, and safety regulation, leading to improved equipment reliability and reduced patient trauma and healthcare costs.