Seven-time Tour de France winner Lance Armstrong is to face charges in the US over claims he used performance-enhancing drugs during his record-breaking career.
The US Anti-Doping Agency has informed the cyclist it has forwarded its allegations to the Anti-Doping Review Board, which will decide whether to proceed with the case.
Armstrong will be banned from competing in his current incarnation as a triathlete while the process takes place - and could be stripped of his record seven Tour titles if found guilty of the resulting charges.
He has never failed a drug test and having repeatedly denied ever cheating, he issued a strong statement rejecting the latest claims.
"I have never doped, and, unlike many of my accusers, I have competed as an endurance athlete for 25 years with no spike in performance, passed more than 500 drug tests and never failed one," the statement said.
"(The) USADA, an organisation largely funded by taxpayer dollars but governed only by self-written rules, intends to again dredge up discredited allegations dating back more than 16 years to prevent me from competing as a triathlete and try and strip me of the seven Tour de France victories I earned.
"These are the very same charges and the same witnesses that the Justice Department chose not to pursue after a two-year investigation.
"These charges are baseless, motivated by spite and advanced through testimony bought and paid for by promises of anonymity and immunity."
Five of Armstrong's associates, three doctors and two team officials, were also told that proceedings had begun against them in what could be one of the biggest doping cases in sport.
The Texan was also accused of trafficking and administering drugs to other cyclists as well as conspiring with team manager Johan Bruyneel, doctor Pedro Celaya, doctor Luis del Moral, doctor Michele Ferrari and trainer Jose Pepe Marti.
The USADA said in a statement: "This formal notice letter is the first step in the multi-step legal process for alleged sport anti-doping rule violations.
"As in every USADA case, all named individuals are presumed innocent of the allegations unless and until proven otherwise through the established legal process."
Armstrong was dogged by accusations of cheating and foul play during his career.
The US Justice Department spent two years investigating the claims against him but closed their case in February without laying any charges against him.