Hamilton Standard has been working on one EVA system concept which responds to NASA's design reference mission for the manned exploration of Mars early in the 21st century. Our concept uses a robotic support cart, to allow a simpler and lighter space suit and life support system. This, together with use of Martian resources, has shown the potential to satisfy mission needs. Present work includes preliminary design studies, analyses, and fabrication of a functional mock-up including the pressure garment, life support system, suit donning stand, and support cart. This paper describes our EVA system concept, the results of preliminary design analyses, and mock-up system tests, as well as some of the issues and challenges involved..