Conchita Wurst stole the show at Europe's biggest charity event, despite plenty of big-name competition. Party-goers dressed in little more than body paint rubbed shoulders with men in tuxedoes and cross-dressers in wild costumes, transforming Vienna's City Hall into a fantasy land.
The occasion, Europe's biggest charity event, was serious - raising money for AIDS research.
"I feel so poorly dressed," quipped a black-suited Bill Clinton, glancing down from the stage at the feather boas, fantastic head-dresses and exotic outfits among the 4,000 or so ball goers.
The former president urged all attending not to forget what lies behind "all the joy of this evening: the determination of every person ... here to give every child a better chance".
U2 will allow fans to download their new single for free in a move that the band hopes will raise more than £1 million to help provide life-saving treatment for people fighting Aids, tuberculosis and malaria.
The rock giants will unveil the track, called Invisible, on a US TV ad for fundraising partnership (RED) to be aired during the Super Bowl on February 2.
Invisible will be made available on iTunes for 24 hours, with the Bank Of America donating 60p for each download, to a maximum of £1.2 million, to the Global Fund To Fight AIDs,Tuberculosis And Malaria.
Bono helped to found the organisation (RED) in 2006, which has gone on to generate more than £145 million for the Global Fund.
Charities have used World Aids Day to call for more to be done to encourage people to get tested for HIV.
It comes as the number of those living with the virus in the UK reaches 100,000, and the reason the virus is spreading faster than it ever has before is because of the the amount of people, estimated at around 20,000, who are unaware of their infections.
Joanna Simpson reports.
The number of people diagnosed with HIV in the UK has reached a record high, passing 100,000 for the first time, the Terrence Higgins Trust said.
Though the number is "worryingly high" according to Paul Ward from the Terrence Higgins Trust, it is better to have people diagnosed and getting the world class treatment available in the UK, than continuing unaware of their infection.
HIV infection in the UK continues to pose a major health threat to thousands of people, and for the first time, the number of people living with the infection has hit 100,000.
Scientists say ancient viruses inherited from Neanderthals have been found in modern human DNA.
Researchers at Oxford University's Department of Zoology are looking at possible links between the retroviruses, which are hard-wired into our DNA, and modern diseases such as Aids and cancer.
Around 8% of human DNA is made up of such retroviruses, which are passed from generation to generation.
It is thought they may have originated from an ancestor common to both Neanderthals and early humans more than half a million years ago.
An estimated 25,000 Britons are infected with HIV and don't know it, the Health Protection Agency has announced.
The figure has prompted the Prime Minister to mark World Aids Day by calling for better education about HIV-AIDS to stop preventable deaths, as ITV News's Martha Fairlie reports:
There is a stark warning on World Aids Day that 25,000 people in the UK are infected with the HIV virus, without knowing about it. It raises concerns that they are not getting potentially lifesaving treatment early enough and could be passing it on and infecting others.
Experts say the number of cases is actually falling in hotspots such as Africa and America, leading David Cameron to call for better education about the condition and more routine testing. Watch this report from Martha Fairlie.
Paul Ward of the Terrence Higgins Trust has said that there is still more to be done in the fight against HIV and Aids.
Speaking before a service to mark World Aids Day, Mr Ward told ITV News; "the real challenge we've got is the 25% of those people who have not been diagnosed. What we would like to see is... much more work to expand the access and make it much easier to take an HIV test."