A Soyuz capsule carrying two Russian cosmonauts and an American astronaut has left Earth bound for the International Space Station (ISS).
Lift-off from the Baikonur cosmodrome in southern Kazakhstan occurred at the scheduled time of 0510 (2310 GMT).
Alexander Kaleri, Oleg Skripochka and Scott Kelly are due to reach the orbiting platform on Saturday.
The men will complete a five-month tour of duty aboard the laboratory as part of the Expedition 25 and 26 crews.
Assuming the February flight of the US shuttle Endeavour is not delayed, Scott Kelly will be joined in orbit by his brother, Mark - the first time that siblings have been in space together.
Scott Kelly will act as a flight engineer on Expedition 25, before assuming command of the orbiting platform with the Expedition 26 team.
The rest of the 26 team, due to launch in December, includes Paulo Nespoli, Europe's next long-duration ISS resident.
The next shuttle mission will be undertaken by Discovery next month. It will carry a storeroom to the station.
Endeavour's task will be to deliver the Alpha Magnetic Spectrometer, a particle physics experiment.
US legislators want the US space agency to add one further flight to the shuttle manifest next year before the orbiters are put in museums. If this goes ahead, the mission, to loft spare parts for the ISS, would most probably be completed by the Atlantis ship.
Once the shuttles are retired, the only way of getting people to the station in the next few years will be by Russian Soyuz craft.
Expedition 25: Nasa astronauts Commander Doug Wheelock, Scott Kelly and Shannon Walker; Russian cosmonauts Oleg Skripochka, Alexander Kaleriand Fyodor Yurchikhin.
Expedition 26: Nasa astronauts Commander Scott Kelly and Catherine Coleman; Russian cosmonauts Alexander Kaleri, Oleg Skripochka and Dmitry Kondratyev; and Esa astronaut Paolo Nespoli.