An estimated 700,000 people attended the St Patick's Day parade in Dublin today, according to the gardai.
The number attending was significantly up on last year's figure of 500,000.
More than 3000 perfomers entertained the crowds on an unusually warm spring day in the capital.
The Grand Marshals - representatives of four Irish international aid agencies - were applauded as they drove the parade route. The grand marshals were chosen as a way to say thank you to the people of Ireland for their overwhelming response to the recent catastrophic tsunami.
Marching bands flew in from the US and UK, while school students were dressing up as stilt-walking fish and giant bicycles.
"It's the day when everyone wants to see what's going on in Ireland," Nik Quaife, spokesman for the St Patrick's Festival, said.
An Italian flagwaving troupe from Trieste joined street theatre and carnival groups for the parade, which has the theme of Mischief, Mayhem and Madness.
In a break with tradition the parade is travelled from Parnell Square to Patrick Street.
Other events taking place include a massive outdoor ceili and a concert at the Temple Bar Music Centre by Belfast-born DJ David Holmes.
Organisers are asking people to enjoy themselves responsibly after claims that drunkenness marred last year's festival.
President Mary McAleese, in her St Patrick's Day message, said that the festival reminded people of their membership of a remarkable global family. "As our global Irish family and friends celebrate this day through the expression of our culture and heritage in our language, literature, games, poetry, music and dance, I hope that the legacy of St Patrick will long encourage us to treasure our strong community spirit and tradition of welcome and care for one another," she said.
There will also be parades nationwide and others as far afield as Russia, New York, Seoul, Tokyo, Denmark, Sydney, Toronto, Munich, the Caribbean and Barcelona.