Muslim Brotherhood leader Mohammed Badie and 682 other supporters of ousted President Mohammed Morsi are standing trial in central Egypt.
They face charges including the murder of several policemen during a crackdown on the Islamist movement in August.
Most of the defendants are being tried in absentia and officials said Mr Badie was not in court for security reasons.
The mass trial in Minya province comes a day after the same court sentenced 528 other Morsi supporters to death.
There has been widespread condemnation of the sentences, which were delivered on only the second session of the trial.
The Egyptian authorities have cracked down on the Brotherhood since the military overthrow Mr Morsi in July. More than 1,000 people have been killed and thousands of others arrested.
Mr Badie, the Brotherhood’s general guide, is being detained along with dozens of other senior leaders of the Islamist movement.
The military stepped in after months of street protests against Mr Morsi – Egypt’s first democratically-elected president.
Following Mr Morsi’s removal from office the Brotherhood set up protest camps in Cairo, at which Mr Badie was a prominent figure.
Police eventually dispersed the camps, killing hundreds of protesters, and Mr Badie went into hiding. He was detained in August.
Mr Badie’s 38-year-old son Ammar was among those killed in the protests.
The Brotherhood and human rights groups denounced Monday’s death sentences.
The verdicts must now go to Egypt’s supreme religious authority, the Grand Mufti, for approval or rejection.
Analysts say that although death sentences are often handed down in Egypt, few have been carried out in recent years.
All of those convicted on Monday are expected to appeal.
The Brotherhood has been declared a terrorist organisation and authorities have punished any public show of support for it.
Source: BBC