This paper summarizes a technology roadmap for completing advanced development of a Proton Exchange Membrane (PEM) Regenerative Fuel Cell (RFC) to meet long life (20,000 hrs at 50% duty cycle) mobile or portable power system applications on the surface of the Moon and Mars. Development of two different sized RFC power system modules is included in this plan (3 and 7.5 kWe). A conservative approach was taken which includes the development of a Ground Engineering System (GES), Qualification Unit (QU), and Flight Unit (FU). Development of a long life system was estimated to require about 7 years (through flight qualification). This development plan was formulated as part of a NASA Lewis task order contract (NAS3-25808) entitled “Mars Power System Concept Definition.” This paper includes a concept description, technology assessment, development issues, development tasks, and development schedule.