Democrat and Republican candidates seeking their parties' nominations for this year's presidential election in the US face their first formal test tonight.
The Iowa Caucus gets under way at around midnight Irish time.
Opinion polls indicate no clear leader in either party race.
The Iowa Caucus has held a special place in modern US elections, and with the open nature of the Presidential race this time around, it has been the focus of unprecedented political attention.
On the Democratic side, Iowa has challenged Senator Hillary Clinton's position as the national front runner.
Most polls show the former first lady practically tied with former Senator John Edwards and Illinois Senator Barack Obama.
Some pollsters are not ruling out the possibility that tonight's Caucus could result in no clear winner.
On the Republican side, the race seems spilt between former Arkansas Governor Mike Huckabee and the former Governor of Massachusetts, Mitt Romney.
Senator John McCain, whose campaign has experienced a resurgence, is trailing third.
Voting starts around midnight Irish time, with results expected some hours later.
