Comparative tests were performed by Boeing, Marshall Space Flight Center (MSFC) or Boeing subcontractors to select the optimum technology for waste water processing on Space Station Freedom (SSF). A Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES) and a Vapor Compression Distillation Subsystem (VCDS) were built and tested to compare urine processing capability. A portion of the distillate recovered from pretreated urine; ie, the water which originates in the resupply food, is the basis for closed loop life support on SSF. Several other waste water “Challenge Solutions”, representing laboratory experiment waste water, were also comparatively processed with these two technologies. Performance, water quality and specific energy were compared for conceptual designs intended to function as part of the Water Recovery and Management (WRM) system. The VCDS was chosen as the optimum technological design for the Environmental Control and Life Support System (ECLSS) Urine Processor (UP) by Boeing Aerospace & Electronics which is under contract to NASA to build Work Package 01 (WP01) for SSF.