Fourteen political parties are fighting for the 550 seats in Parliament. The AK Party, a religious party headed by Prime Minister Recip Tayyip Erdogan, holds the largest bloc of seats.
Erdogan has been campaigning on economic growth. But the BBC reports that many Turkish voters see the election as a test of the secular institutions created by Mustafa Kemal Ataturk after the fall of the Ottoman Empire.
Many of the 42 million eligible voters planned to interrupt or return early from holidays to vote.
Secular parties and the military, a stronghold of secularism, blocked Erdogan's choice for president. Erdogan has proposed a number of constitutional changes, including direct election of the president.
Turkey's effort to join the European Union is also expected to be an issue.
Turkey's population is overwhelmingly Muslim. Unlike other nations in the Middle East, the country has not written Islamic laws, like the ban on alcohol, into secular law.