With voting booths set to close at 6pm around Australia - from 8pm onwards NZ time - the finish line is in sight for Prime Minister Julia Gillard and Opposition Leader Tony Abbott after five weeks of frenetic campaigning.
The federal election result is expected to be one of the closest in living memory.
After starting the day in Sydney, Ms Gillard went to Seabrook primary school in Melbourne's south-west in the afternoon to cast her ballot.
She has now gone home to Altona for a break before driving to a city hotel where she will watch the count with family members.
Mr Abbott cast his vote at the Queenscliff surf-lifesaving club in his Sydney electorate of Warringah on Saturday morning.
The news from Afghanistan of the deaths of two Australian soldiers cast a shadow over the day. Both leaders expressed their sympathies to the bereaved families.
Media polls show tight contest
An extensive Nielsen poll in Fairfax newspapers puts Labor just ahead on 52 points to the Coalition's 48 on a two-party-preferred basis - but that might not be enough to ensure a victory for Prime Minister Julia Gillard. On primary votes, the Coalition's lead is 41.5% to 39%.
A Newspoll in the Weekend Australian newspaper shows an even tighter contest. It has Labor at 50.2% to the Coalition's 49.8% on a two-party-preferred basis.
But Labor's primary vote is given as 36.2%, with the Coalition on 43.4% and the Greens on 13.9%.
Deputy Prime Minister Wayne Swann says that he's not expecting a quick result and that it's likely to be a photo finish.
Hung Parliament a possibility
Labor says it expects to lose seats, but the ABC reports it is not clear if the Coalition will gain enough ground to win the 17 seats it needs to form a government in its own right.
The presence of three independents in the Lower House means Labor has to lose only 13 of the notional 88 seats it holds for a hung Parliament to come into play.
Queensland could hold the key to the election. Sixteen of its 30 seats in the federal House of Representative are held by a margin of less than 5%.
Voting is compulsory in Australia.