Just before liftoff from Kennedy Space Center, Launch Director Mike Lienbach wished the six crew members "good luck and Godspeed" and told them to "have some fun out there."
Atlantis reached orbit without incident and was on its way toward the space station at about 17,500 mph, NASA said. The three main engines were shut off and Commander Ken Ham and his crew were to use smaller orbital maneuvering system engines to lift the shuttle higher into space for its two-day pursuit of the space station.
Atlantis lifted off and cleared the launch tower at 2:20:50 p.m. EDT and at 2:23:33 p.m. the twin solid rocket boosters fell away as designed, allowing the three main engines to push the spacecraft faster and higher.
In the minutes leading to liftoff, NASA engineers resolved concerns about the discovery of a ball bearing near the shuttle's payload bay.
The all-male shuttle crew members are on a 12-day mission to deliver an integrated cargo carrier and a Russian-built research module. The are to return to Earth May 26.
Just two shuttle flights are scheduled after Atlantis lifts off -- one flight by Discovery and one by Endeavour. NASA plans to end the 3-decade-old program by the end of this year.
The station is to remain operational until at least 2020 with NASA astronauts reaching it via Russian Soyuz spaceships until private companies develop spacecraft that can reliably ferry people into space.