Opinion polls suggest the Justice and Development (AK) party of Recep Tayyip Erdogan, the current prime minister, will win the elections, giving them five more years in power.
But the size of its majority will be important.
About 43 million Turks out of a population of 74 million are eligible to vote.
In the last elections in 2002 only two parties cleared the 10 per cent hurdle for seats in Turkey's parliament, ensuring an almost two-thirds majority for the AK party.
But the Nationalist Movement party (MHP) and the Republican People's party (CHP) look likely to clear the barrier.
If they do, it is expected to cost the AK party parliamentary seats.
The next government will have to tackle rising Kurdish separatist violence in the east and decide whether the army can enter northern Iraq to crush Turkish Kurdish fighters based there - a move that is increasingly worrying the US.
It must also find a compromise candidate for president and speed up EU-inspired reforms or risk an economic backlash.
Analysts say this election is one of the most important in a quarter of a century because it is pivotal to Turkey's future direction.
Opposition parties say the vote is about defending Turkey's secular system against political Islam, though Erdogan laughs off CHP claims that he wants to turn Turkey, which bridges Europe and the Middle East, into an Iranian-style theocracy.
Some independent, mostly pro-Kurdish candidates are also tipped to win seats in the 550-member parliament.
The AK party's record of economic growth of seven per cent a year on average, falling inflation and record foreign investment has won over many Turks fed up with mismanagement, corruption, fractious coalitions and four military coups in five decades.
The party also secured coveted EU accession talks in 2005 after 40 years of trying.
Erdogan has said he will leave politics if his party fails to win an absolute majority.