Tokyo triumphed in the contest to host the Olympics and Paralympics in 2020 after seeing off rivals Madrid and Istanbul in dramatic circumstances.
The Japanese city won convincingly in the end - with doping scandals perhaps proving costly to both Madrid's and Istanbul's hopes.
Britain's International Olympic Committee member Adam Pengilly quizzed officials from both bidding cities about doping issues in Spain and Turkey during the final presentations here in Buenos Aires.
Tokyo, the capital of Japan - a country that has never had a positive test by an athlete in either the Olympics or the Paralympics - went on to win the IOC vote comfortably, beating Istanbul by 60 to 36 votes in the final round after Madrid had been eliminated.
IOC president Jacques Rogge said afterwards: "It is clear that the IOC members pay a lot of attention to the situation in the fight against doping.
"However it's very difficult to assess if it has played a major role in the voting itself."
Pengilly, a former skeleton racer, raised questions about the recent doping scandal that has seen more than 30 Turkish athletes test positive, and over Operation Puerto in Spain where a court has ordered that dozens of possibly suspect blood bags belonging to sports stars be destroyed rather than be tested.
Rogge did not vote himself but said that Tokyo would be a "safe pair of hands" and added: "As a surgeon, that's something that appeals."
Meanwhile, Tokyo's victorious Olympic bid chiefs promised to try to emulate the passion of the London 2012 Games when they become hosts in seven years' time.
Tsunekazu Takeda, the former Olympic showjumper who is now head of the Japanese Olympic Committee (JOC), said: "London was a fantastic Games, putting the athletes first, the facilities were wonderful and the volunteers were so eager to have a superb Games.
"The people of the UK were all fully supporting the London Games and we felt their passion for the Olympic Games and that's something we would like to replicate in Tokyo in 2020."
It will be the second time the Japanese capital has hosted the Games having previously done so in 1964.
Tokyo won by 60 votes to 36 in the final round against Istanbul and the victory came despite some IOC members expressing concern over leaks at the Fukushima nuclear plant - which is a full 150 miles from the capital.
Japan's Prime Minister Shinzo Abe tackled the issue head-on in Tokyo's final presentation, promising the IOC: "I shall take the responsibility to implement programmes to render this situation completely problem-free and I say that most emphatically and unequivocally."
Tokyo's cause was helped in no small way by the presence of Cambridge-educated Princess Hisako of Takamado, and a bravura performance in its final presentation by Paralympic athlete Mima Sato.
Hisako, the first member of the Japanese Imperial family to have ever addressed the IOC, delivered Tokyo's opening speech of the presentation and pushed all the right buttons.
Sato, who lost a leg following bone cancer and competed in the long jump at the London 2012 Paralympics, said: "What we have seen is the impact of the Olympic values as never before in Japan. And what the country has witnessed is that those precious values - excellence, friendship and respect - can be so much more than just words."
For Istanbul, bidding for the fifth time, there was bitter disappointment yet again.
The Turkish city had been the frontrunner for so long but suffered a series of damaging blows later in the campaign: the protests in Taksim Square - a proposed Games venue - in June, a major doping scandal, the jailing of political opponents and journalists last month and the rising threat of war in next-door Syria.
Turkey's Prime Minister Recep Erdogan tried to address the issue, telling IOC members: "We live at a time when our region and the world crave for peace.
"And at this critical moment, we would like to send a strong message of peace to the whole world from Istanbul, the city of friendship and brotherhood."
Tennis player Feliciano Lopez, who represented Spain at London 2012, reacted angrily to the outcome.
He told AS.com: "What a disgraceful decision from the IOC, which has shown once again to have no regard for fair play and values all other interests above sport.
"I would like to believe that corruption, the economic situation and Operation Puerto were all key to us losing out, but I still don't understand it.
"What about the 30 Turkish athletes who were implicated in doping? This doesn't add up. And what about the nuclear crisis of Fukushima? Every candidate had its problems."