Nike said it would continue to support Livestrong.
Beer-maker Anheuser-Busch did not give a reason for its action, which followed hours later. A two-sentence statement from U.S. marketing vice president Paul Chibe said simply, "We have decided not to renew our relationship with Lance Armstrong when our current contract expires at the end of 2012. We will continue to support the Livestrong Foundation and its cycling and running events."
The U.S. Anti-Doping Agency released a massive report last week detailing allegations of widespread doping by Armstrong and his teams when he won the Tour de France seven consecutive times from 1999 to 2005.
The document's purpose was to show why USADA has banned him from cycling for life and ordered 14 years of his career results erased - including those Tour titles. It contains sworn statements from 26 witnesses, including 11 former teammates.
Armstrong, who was not paid a salary as chairman of the Lance Armstrong Foundation, will remain on its 15-member board. His duties leading the board will be turned over to vice chairman Jeff Garvey, who was founding chairman in 1997.
"This organization, its mission and its supporters are incredibly dear to my heart," Armstrong said in a statement. "Today therefore, to spare the foundation any negative effects as a result of controversy surrounding my cycling career, I will conclude my chairmanship."
Foundation spokeswoman Katherine McLane said the decision turns over the foundation's big-picture strategic planning to Garvey. He will also assume some of the public appearances and meetings that Armstrong used to handle.
Kelley O'Keefe, professor of brand strategy at Virginia Commonwealth University, said that the charity already may be permanently damaged and that Armstrong may never be able to fully resume his public role.
"From the brand perspective, Armstrong is done," O'Keefe said.
O'Keefe compared Armstrong with Tiger Woods and Michael Vick, who also were embroiled in controversy but were able to return to the playing fields to help redeem their image.
"Armstrong doesn't have that. He's just a retired athlete with a tarnished image," O'Keefe said.
Armstrong strongly denies doping, but did not fight USADA accusations through arbitration, saying he thinks the process is unfair. Once Armstrong gave up the fight in August and the report came out, crisis management experts predicted the future of the foundation, known mainly by its Livestrong brand name, would be threatened. They said Armstrong should consider stepping down.
Armstrong's inspiring story of not only recovering from testicular cancer that had spread to his lungs and brain but then winning the world's best-known bike race helped his foundation grow from a small operation in Texas into one of the most popular charities in the country.
Armstrong drew legions of fans - and donations - and insisted he was drug-free at a time when doping was rampant in professional cycling. In 2004, the foundation introduced the yellow "Livestrong" bracelets, selling more than 80 million and creating a global symbol for cancer awareness and survivorship.