The media magnate who is also the country's richest man is facing a stiff challenge from the opposition coalition led by the centre-left former prime minister Romano Prodi during two days of voting that end on Monday at 1300GMT.
Due to Italian election laws, opinion polls have not been published for the past two weeks but past surveys have indicated that Berlusconi has generally trailed Prodi during the past two years.
Before a ban on campaigning came into force on Saturday both candidates used their final rally speeches to make appeals to voters.
Berlusconi hopes his promises of tax cuts can bring a surprise victory for him and his Forza Italia party.
He has consistently attacked Prodi's choice of coalition partners that range from Catholic parties to liberals and communists.
In his final election speech on Friday in Naples, the 69-year-old owner of Mediaset and AC Milan likened his centre-left opponents to Stalin and Pol Pot and said Italy's "Christian identity" was at stake.
He said the country faced a fundamental choice between "an Italy of taxes, an Italy of pessimism" and "an Italy of freedom and rights, of tolerance ... above all an Italy of love - that's our Italy."
Over 50 million Italians are
eligible to vote over two days
Prodi, who was prime minister from 1996 to 1997 before becoming president of the European Commission, has campaigned on a call for national unity, promising tax breaks for Italian companies and to withdraw troops from Iraq as soon as possible.
At his final rally in Rome, the 66-year-old said: "Italians need change, and we can do it in the most democratic way possible, with a pen and a ballot."
The rancour that has accompanied this year's contest has surprised Italians.
Among the insults doled out by both sides, often live on television, included Prodi likening Berlusconi to a drunkard clinging to a lamppost and the prime minister retorting that his opponent was a "useful idiot".
A new voting system was rushed into law in December meaning that whoever wins is likely to enjoy a smaller parliamentary majority than the outgoing administration.
That has raised fears of a return to "revolving-door" leadership that Berlusconi ended by becoming the head of Italy's longest serving post-war government in 2001.
There have been 60 administrations since World War Two, and coalition instability has often brought down governments within their first year of office.
Around 50 million Italians are eligible to vote.
Prodi, nicknamed Il Professore,
has called for national unity
Italy's interior ministry said 60,000 polling stations around the country were to open from 8 am to 10 pm on Sunday and 7 am to 3 pm on Monday.
First partial results are expected on Monday evening.
On Saturday the foreign ministry reported a 42% turnout among expatriate Italians who have been allowed to vote for the first time in a general election.
Whatever the result, political analysts expect it to take at least a month before a new government can be formed.