Indonesians have cast their ballots to elect representatives in national and local parliaments.
Some 19,000 seats are being contested across the nation, including the 560 seats in the national parliament.
The polls will determine which parties can field candidates for the presidential election on 9 July.
The opposition Democratic Party of Struggle is expected to do well. Its candidate, Joko Widodo, is seen by many as Indonesia's next president.
Mr Widodo, the Jakarta governor who is popularly known as Jokowi, has proven to be a hit with voters because of an approachable and down-to-earth image.
He told reporters at a polling station in Jakarta he believed his party would perform strongly.
"I'm very confident that my party will do very well,'' he said.
Voting is taking place across three different time zones, however, election officials have already warned of possible delays with the vote.
One official for Papua province, Betty Wanane, told the AFP news agency that planes carrying ballots could not reach dozens of districts in mountainous areas, warning of delays of up to three days.
Parties wishing to field candidates in the presidential polls must either secure 20% of the seats in parliament or 25% of the total vote.
Candidates whose parties fail to meet these thresholds must form or enter a coalition before they can run for president.
The ruling Democratic Party of Indonesian President Susilo Bambang Yudhoyono is expected to see its support fall, amid a raft of corruption scandals.
Mr Yudhoyono, meanwhile, is constitutionally barred from seeking a third presidential term.
Mr Widodo's main challengers are currently expected to be businessman Aburizal Bakrie of Golkar - one of Indonesia's largest and oldest political parties - and former military general Prabowo Subianto of the Gerindra party.
Indonesia is the world's largest Muslim nation and South East Asia's biggest economy.
Some 187 million Indonesians are eligible to vote, with nearly 22 million people voting for the first time.
The country has declared Wednesday a public holiday to encourage high voter turn-out.
The polls are expected to be largely peaceful despite fears of violence in the western Aceh province following a series of politically-linked attacks last week.