Hosni Mubarak trial: Egypt ex-president back in court
Mr Mubarak, 83, faces the death penalty if found guilty of ordering the killing of protesters in this year's uprising.
He is also accused of corruption. The former leader - who was again wheeled into the courtroom on a hospital bed - denies all the charges.
Mr Mubarak is being tried with his sons Alaa and Gama, who are accused of corruption and also deny the charges.
Mr Mubarak was forced from office by mass demonstrations in February.
Tantawi demand
Hundreds of riot police were on guard outside the courtroom on Monday.
A number of Mubarak supporters had gathered, some chanting: "He is Egyptian until death" and "Hosni Mubarak is not Saddam". Scuffles broke out at regular intervals with anti-Mubarak protesters.
A military helicopter landed at the site, carrying Mr Mubarak. State television showed the former president, wearing a blue jumpsuit, being wheeled out of an ambulance on a hospital bed. His son Alaa tried to cover the camera.
In court, presiding Judge Ahmed Refaat asked if the defendants were present, starting with Mr Mubarak, then his two sons.
As in the first hearing, the judge again appeared to struggle to maintain order, referring to the fact there were more than 100 lawyers. He repeatedly asked them to take their seats.
The session is likely to be dominated by legal arguments.
Lawyers for the families of the demonstrators who were killed in the uprising have already asked for greater access to Mr Mubarak's communication records, the BBC's Yolande Knell in Cairo reports.
The families want to know what orders he gave to his officials as police tried to stop the protests using brutal means, our correspondent says.
Defence lawyers have demanded that Field Marshal Mohamed Hussein Tantawi, who leads the military council that took over from Mr Mubarak but who was his defence minister for two decades, must testify.
They say his evidence on Mr Mubarak could prove pivotal.
The judge has still to rule on who will testify.
Mr Mubarak's lawyer, Farid al-Deeb, has asked the judge to call 1,600 witnesses. Observers say the judge will probably reduce the list he has demanded.
Mr Mubarak is reported to be in a poor state of health, and doctors have been constantly monitoring his medical condition at a military hospital near the capital.
Blogger questioned
During the previous court session on 3 August, some 3,000 soldiers and police were drafted in to maintain order.
Mr Mubarak's first appearance in court shocked the nation
Despite that, the court session was at times unruly, with lawyers jostling and clamouring to be heard by the judge.
The charges against the Mubaraks were read out, and Hosni Mubarak and his sons each denied them.
Everybody was in shock as the trial began, says the BBC's Jon Leyne in Cairo, because this was the moment that no-one in Egypt - maybe all of the Middle East - expected to see.
On Sunday, Egypt's former Interior Minister Habib al-Adly reappeared in the Cairo court on charges of killing nearly 850 demonstrators during the uprising. His trial was adjourned to 5 September.
Adly has already been sentenced to 12 years in prison for money-laundering.
In a separate development, leading Egyptian blogger Asmaa Mahfouz was on Sunday questioned for allegedly defaming the military on Facebook, the official Mena news agency reported.
Ms Mahfouz, one of the leader of the Egyptian revolution, is suspected of calling for assassination attacks against the military and judicial bodies.
She was briefly detained by military prosecutors and later released on a bail of $3,356 (£2,062), Mena says. Her lawyer denied all the accusations.