Human missions to Mars will represent not only a departure from the relative protection and proximity of low Earth orbit but also the way space missions are currently conducted. Traveling at 180,000 miles per second, radiofrequency communication will require up to 20 minutes to reach Mars from Earth. Extended periods of communication blackout may leave the Mars-nauts without Earth contact for weeks. Crews will be on their own to recover from mission complications, including serious crew member illness or injury. These conditions dictate unique applications of telemedicine.