He is being tried in Milan with 13 other people, including David Mills, a British lawyer specialising in off-shore tax advice and the estranged husband of Tessa Jowell, the British culture secretary.
If convicted of the most serious charge, tax fraud, he could face up to six years in jail.
Berlusconi, 70, had kept a low profile since April's general election defeat to Romano Prodi, but the case involving the broadcast company, controlled by his family, has returned him to the public's attention.
He denies any wrongdoing and has accused his critics of bringing the charges against him for political gain.
Prison sentence
Berlusconi has previously been involved in many legal cases and was once given a prison sentence for false book-keeping at a film production company and for paying bribes to tax inspectors, but he was later acquitted on appeal.
He is not expected to attend the opening sessions of the trial, which is expected to last for months and possibly years. Tuesday's hearing is expected to be largely procedural.
He was quoted on Tuesday as saying he would not lead Italy's government if his centre-right coalition is returned to power.
Berlusconi was quoted by Libero newspaper as telling a group of friends: "We will certainly return to power but I can already tell you something. Whatever happens, I will not go back to Palazzo Chigi (the prime minister's office)."
Berlusconi first amassed a fortune through real estate before later moving into politics, founding the Forza italia party and twice becoming prime minister.
He has a wide range of business interests varying from publishing to and being the owner of the AC Milan football club.