Voting has ended in the constituency of Sonia Gandhi, the president of India's ruling Congress party, who is standing for re-election.
Sonia Gandhi's daughter, Priyanka, has led her campaign
Mrs Gandhi resigned from parliament in March, following allegations that she was profiting from another public post.
Voting has also ended in two states and one union territory to elect a new legislative assembly.
The states are West Bengal, which has the world's longest running elected Communist government, and Tamil Nadu.
Extra security has been deployed in the parliamentary constituency of Rae Bareilly, in the northern state of Uttar Pradesh, from where Mrs Gandhi is seeking re-election.
Despite facing a candidate of the main opposition Bharatiya Janata Party, she is expected to win easily from the seat that has been a stronghold of her family.
"What we have to see is the size of the majority - she won by 240,000 votes last time - we have to see if it goes up or down," political analyst Mahesh Rangarajan is quoted as saying by AFP.
Her children, Rahul Gandhi - himself an MP - and Priyanka have been heavily involved in the campaign.
Sonia Gandhi held the Rae Bareilly seat before quitting in March, following a controversy over her role as head of the National Advisory Council, a state-funded body set up to advise the current government.
Under Indian law, MPs may not gain financially from other public posts.
Tamil Nadu votes
Separately, some 43.6 million people are eligible to vote in elections in the southern state of Tamil Nadu, one of the country's most economically developed regions.
Tamil Nadu Chief Minister Jayalalitha is hoping to win another term
The voters will determine the fortunes of Tamil Nadu Chief Minister Jayalalitha, a former film actress and one of India's most controversial politicians.
Ms Jayalalitha, who heads the regional AIADMK, spent two months in jail in 2001 after being convicted for corruption, a ruling which was later overturned.
The AIADMK is being opposed by the DMK party, which is a member of India's Congress-led governing coalition.
The keenly contested campaign was marked by freebies offered to voters by both parties if elected, including television sets, cooking stoves, electricity, rice, bicycles and even gold.
Voting is also taking place in neighbouring Pondicherry, which was once a French colony, and West Bengal - where voting has been spread over five phases to prevent violence.
West Bengal's ruling Communist-led Left Front government is widely expected to be re-elected for a record seventh term.