The National Aeronautics and Space Administration (NASA) has been challenged to develop capabilities designed to meet the unique challenges required to explore the solar system and is working toward a goal of landing humans on near-Earth asteroids, the Moon, and eventually Mars. 1 The current plan for NASA is to support the extension of the International Space Station (ISS) through 2020. The ISS will serve as a platform for space life sciences research as well as preparation for future exploration class missions by further increasing our understanding of space physiology. 2,3 The primary objectives in sending humans back to the lunar surface or to Mars are to explore, perform research, and gain knowledge. The safeguarding of human health and performance, using appropriate medical care, is essential to meet these mission objectives. History has shown that during the exploration of frontiers on Earth, human physiologic maladaptation, illness, and injury have accounted for more failures of expeditions than any single technical or environmental factor. 4 Carrying out this bold vision creates many new challenges, including a level of medical autonomy unprecedented for human spaceflight. Because a prompt evacuation back to Earth is not feasible in exploration missions, the capability of delivering medical care on site will be the key to success. 5 However, it will be impossible to provide medical care for all imaginable problems. The crew will, therefore, need improvisational skills and acceptance of a certain amount of risk. This paper focuses on the medical and communication challenges of exploration type missions and explicates the value of combined emergency medicine (EM) and wilderness medicine (WM) training for astronaut physicians. Communication Challenges and Self-Sufficiency The time to reach definitive medical care from the ISS may be as brief as 24 hours, but from a lunar base, it would be at best several days. Assuming there are no major developments in propulsion technology, even a Mars "fly-by" with direct return to Earth may represent a 9-month round trip. The entire trip may last as long as 1000 days. Radio communication will require up to 20