Where Ireland may once have been a musical backwater, Oxegen delivers some of the biggest international and Irish acts.
English singer Lily Allen was spotted walking through the campsite before her slot on Friday night. Accompanied by a bodyguard, Allen was said to be in search of Monaghan relatives who she gave a shout out to during her later set.
Elsewhere in the same campsite, under cover and under canvas, Westlife's Mark Feehily had pitched his own tent.
He said: "I come every year and I usually bring my tent. I don't mind the rain. For me it's the perfect break before it gets busy with Westlife. The music is brilliant."
The remainder of the big names – including American singer Lady GaGa – chose more luxurious accommodation in the nearby Louis Fitzgerald hotel.
Arriving on site before their sets, the performers rubbed shoulders with the likes of newly published author Amy Huberman and her fiancée, Irish rugby captain Brian O'Driscoll in the VIP area. A few tables away sat Caleb Followill, front man of last night's headliners Kings of Leon, with his girlfriend, model Lily Aldridge.
In the light of three cases of suspected swine flu at last month's Glastonbury festival, the HSE had been so concerned about such a large number of people gathered from all over the country in one location that a number of isolation facilities were set up backstage and a supply of the anti-viral Tamiflu was available if needed.
At the time of going to print there were no reported cases.