Swimming's world governing body FINA has dropped its investigation into the results of a doping test from Ian Thorpe after he was cleared of any offences.
Thorpe was investigated by the Australian Sports Anti-Doping Authority (ASADA) after a random drug test taken last year showed unusually high levels of naturally-occurring hormones.
FINA (International Swimming Federation) had also launched a separate investigation but said there was no point pursuing it after ASADA found in August that Thorpe had no case to answer.
"We are not continuing the case," FINA executive director Cornel Marculescu said.
"There's not sufficient evidence to take further action.
"We have informed CAS (the Court of Arbitration for Sport) and ASADA."
Thorpe, who won five Olympic gold medals before his retirement last year, has always maintained his innocence but claimed the publicity surrounding the case had tarnished his reputation and he planned to take legal action once the case was closed.
The initial investigation was launched after a random sample taken from Thorpe in May 2006, shortly after he had undergone surgery to repair a broken hand, showed slightly elevated levels of testosterone and leutenising hormone.
Both substances are naturally occurring and ASADA said it was common for athletes to show slightly elevated levels without any suggestion of an offence.
Thorpe was tested hundreds of times over a career spanning more than a decade but never failed a test.
His case became public knowledge in March this year when the leaked test results were published by a French newspaper, prompting the World Anti-Doping Agency to tighten their privacy provisions to avoid any further breaches of confidentiality.
Thorpe burst on to the world stage as a 15-year-old at the 1998 world championships and went on to become one of the sport's greatest competitors.
He won three gold medals as a 17-year-old at the 2000 Sydney Olympics and the 200 and 400 metres freestyle double at the 2004 Athens Olympics.
He still holds the world record for 400 metres freestyle.
Thorpe took a year off training after the Olympics to recharge his batteries but never competed at international level again before announcing in November 2006 that he was retiring because he had lost motivation and wanted to do something else with his life.