Health of space explorers is a requisite for success of human exploration missions and, potentially, for return of explorers to Earth. Continuous, long term existence and complex, potentially hazardous tasks in space environments will challenge health of explorers. Immediate return to Earth will not be possible. Health care systems are being designed to address these concerns, starting from the requirement to maintain health of crew members throughout all mission phases, and the assumption that clinical (medical), preventive, and occupational health care will be necessary in space as on Earth. Systems for medical care, health monitoring and countermeasures, and environmental monitoring and countermeasures are being designed. Basic system definition concepts include an individual crew member, a crew surgeon, remote consultation, equipment, and work area or volume within space habitats that is dedicated for health care. Protocols developed for and adapted from Earth based operations offer specific space operations designs, and may offer a practical alternative to design of unique, highly automated devices for space systems. Guidelines for analog health care facilities on Earth are being used to provide work volume (area) estimates for preliminary space system designs. Dedicated work volume is seen to represent the intersection of system and operations design. For exploration missions, on site expertise and capability, augmented by protocols, computer-based decision support and remote communication, are needed.