STS-71 "Atlantis" (June 27 to July 7, 1995), was the first Space Shuttle mission to dock with the Russian Space Station Mir, and involved an exchange of crews. The "Atlantis" was modified to carry a docking system compatible with the Russian Mir Space Station. Dunbar served as MS-3 on this flight which also carried a Spacelab module in the payload bay in which the crew performed medical evaluations on the returning Mir crew. These evaluations included ascertaining the effects of weightlessness on the cardio/vascular system, the bone/muscle system, the immune system, and the cardio/pulmonary system. Mission duration was 9 days, 19 hours, 23 minutes and 8 seconds, traveling 4.1 million miles in 153 orbits of the earth.