He flew on the space shuttle Columbia mission in October 1993 to conduct experiments on the effect of microgravity on humans. He spent 119 days aboard the Russian space station Mir from September 1997 to January 1998. He then flew on Atlantis in October 2002 to the International Space Station on an assembly mission, making three space walks. He logged over 143 days in space and 28 hours on space walks. Wolf joined the Medical Sciences Division of NASA's Johnson Space Center in 1983, and was selected as an astronaut in 1990. He has since left NASA.