(CNN) -- Seven-time Tour de France champion Lance Armstrong officially announced his retirement from the world of professional cycling Wednesday, saying that he wants to devote more time to his family and the fight against cancer.
Armstrong, 39, issued a statement saying his "focus now is raising (his) five children, promoting the mission of LIVESTRONG (Global Cancer Campaign), and growing entrepreneurial ventures with our great corporate partners in the fight against cancer."
Armstrong first announced his retirement in 2005, but he then attempted a comeback.
Armstrong's cycling career was marred by allegations relating to the use of performance-enhancing drugs, accusations he has consistently denied.
He submitted to dozens of drug tests after ending his initial retirement in September 2009. He underwent surgery that year after breaking his collarbone in a race in Spain.
At age 25, Armstrong, already a promising cyclist on the pro circuit, was diagnosed in 1996 with testicular cancer, which spread to his abdomen, lungs and brain.
After years of treatment, he returned to claim multiple wins in the Tour de France, cycling's premier event.
He became a high-profile fundraiser for cancer research, and serves as chairman of the LiveStrong Foundation, which has raised tens of millions of dollars for cancer research, education and patient support.
"We're fortunate to have Lance back full-time as a hands-on chairman for LIVESTRONG where he can help us capitalize on the great opportunities for progress that lie ahead." Doug Ulman, president and CEO of the foundation, said in a written statement.
Armstrong is not the only athlete to retire and then change his mind.
The most notable example was Michael Jordan, who left the National Basketball Association in 1993 to play professional baseball.
He later returned to the NBA to lead the Chicago Bulls to three more championships.
Armstrong rode his final competitive race in the Tour Down Under in Australia last month.