Millions of viewers in Europe and the Middle East were expected to take in the three-hour annual show, which has a cult following around the continent for its outrageous outfits and off-the-wall music.
It has also attracted its largest media attention ever according to organisers, with over 2,000 accredited media covering the event at the Olympic Stadium Complex, and between 13,500 and 15,000 spectators in attendance.
The opening ceremony, hosted by Athens - the winner of last year's festival - featured a huge golden orb representing the Greek sun, floating waves, and a marine motif from ancient Greek mythology including sirens, sea nymphs, dolphins and tritons.
Among the countries represented by groups and solo artistes participating in the show are all-time leaders Ireland - who have seven titles but haven't won in a decade - and a host of nations which emerged from the break up of the Soviet Union and Yugoslavia.
Sweden ranks among this year's favourites, having brought back 1991 winner Carola with a pop song titled "Invincible".
The three-hour show is being held
at Athens Olympic Indoor Hall
Hosts Greece is also high in the running with "Everything", a rock ballad sung by 1990s pop diva Anna Vissi in her third Eurovision appearance.
Other favourites include the ballad "Never Let You Go" by Russian heartthrob Dima Bilan, the Romanian dance tune "Tornero", and the folk ballad "Layla" from Bosnia-Hercegovina.
Also in with a chance is the Finnish surprise entry "Hard Rock Hallelujah" by Lordi, a heavily made-up monster band whose hideous masks, horns and on-stage pyrotechnics have turned them into the talk of the town.
The US interest
Serbia-Montenegro will be sitting out the contest - but will retain its right to vote - after the separate Serbian and Montenegrin television networks failed to agree on a song to send to Athens.
Viewers from 35 countries will be
voting by phone and SMSmessage
The dispute has come as Montenegro prepares to hold a referendum on May 21, the day after the Eurovision final, on whether it wants full independence from Serbia.
Viewers from 35 countries in Europe, plus Armenia, Israel and Turkey will be voting by telephone or SMS message to a central database in Cologne, Germany.
Audiences may not vote for the country from which they are calling, even if using a foreign mobile phone number.
Greece earned the right to host this year's Eurovision by winning the 2005 contest in Kiev, with a dance tune titled "My Number One" sung by Helena Paparizou.
Eurovision organisers are currently in talks with American network NBC to export the festival to the United States.