Galway: Crowds of up to 50,000 are expected to turn out for the Galway city St Patrick's parade, which starts at 12.30pm on Friday.
This year's parade theme will relate the story of Queen Maebh and the Táin Bó Cuailgne. The event has been planned by director Breandán Ó hEaghra and artistic director Morgan Cooke, who warn there will be much mayhem and many "unsavoury characters roaming the streets and the armies of Connacht and Leinster tearing lumps out of each other".
Meanwhile, the Aran Islands will host an interdenominational festival with Scots Gaelic psalm singers, Welsh tenors and Irish primary-school sopranos.
Performing in three Celtic languages, the singers from the Isle of Lewis in Scotland, Powys in Wales and An Tór ar Lasadh Presbyterian group from Northern Ireland will participate in a St Patrick's choral event hosted by Áras Éanna, Inis Oírr's arts centre.
They will be joined by Cór Arann, comprising school children from Inis Meain and Inis Oírr, and Cór Inis Oírr adults' choir, with Deirdre Ní Chinnéide. The festival opens on St Patrick's night and continues on Saturday with a choral performance at the island's early Christian church Teampall Chaomhán, and a concert at Áras Éanna. - Lorna Siggins
Cork: Thousands of people are expected to flock to Cork city centre for a weekend of festivities. The parade kicks off on St Patrick's Day at 1pm starting at the South Mall. It will proceed along the Grand Parade into Patrick Street and across Patrick's Bridge to the end of MacCurtain Street on the north side of the city.
This year's grand marshals include the Cork City soccer team and Ireland's latest athletics sensation, 60m hurdles world champion Derval O'Rourke from Douglas.
According to the St Patrick's festival director, Moray Bresnihan, some 2,100 people will take part in the parade, which is themed "Adventures in Wonderland". It will feature groups from all over Ireland, as well as marching bands from the US.
This year's parade will have a multicultural flavour, with groups from Togo, Ivory Coast, Nigeria, Bangladesh and Poland adding to the colour and vibrancy of the occasion. - Barry Roche
Waterford: Around 2,000 people are due to take part in the St Patrick's Day parade in Waterford. At least 40,000 people are expected to turn out to see it.
Starting at the junction of Vulcan Street and the Quay at 1pm, the parade will move towards Reginald's Tower and on to The Mall before travelling along Catherine Street, finishing at the People's Park.
Children will be entertained at the park with a family disco from 2 to 4pm.
Bands will play in John Robert's Square. The Supersize Country Market will take place in the Little St Patrick's Street/Jenkins Lane area. City streets will be closed off from 9.30am on Friday, with diversions put in place.
There will be no access to the centre of Waterford or the Quays area until after 2.30pm.
Limerick: Limerick's annual St Patrick's Day parade is being rerouted this year for the first time in many decades.
The rerouted parade forms part of the broader Springfest 2006, a seven-day festival featuring a wide range of musical events.
More than 50 groups will take part in this year's parade, which will see participants march "uptown" for the first time in decades.
The parade will begin at noon at Mathew Bridge, close to where the parade usually finished in years gone by.
The parade route will continue along Rutland Street and O'Connell Street before finishing up at Barrington Street at around 1.30pm.
The new finishing line is located beside Pery Square, and the area's famous fair will take place immediately after the parade.
This year's parade will be led by two Limerick schoolchildren, the names of whom are due to be announced tomorrow.
The grand marshals were chosen following an art competition, open to primary schools across the city, in which children had to paint a picture of how they imagined Limerick would look like in the future.
The festival runs from 2pm to 6pm on both St Patrick's Day and the following day, Saturday March 18th. - Kathyrn Hayes