Dozens of men and women accused of the rape and abuse of children have gone on trial in one of the biggest court cases in France's legal history.
The trial, which involves 66 defendants and is expected to last four months, is taking place in a specially built hall in the town of Angers, western France.
Some 60 lawyers are taking part and the prosecution case runs to 430 pages, AFP news agency reports.
There are 45 alleged child victims whose ages range from 12 to six months.
France has been horrified by the case, wondering how such widespread abuse could have gone on for so long unnoticed by social workers or the police, says the BBC's Caroline Wyatt in Paris.
Of the 66 defendants, 39 face charges of raping children under 15 and of pimping. A total of 39 men and 27 women are going on trial.
The crimes could incur jail terms of up to 30 years.
Expected to last 4 months
66 people - 39 men, 27 women - on trial for allegedly abusing 45 children
25,000 pages of evidence stored on CD-Rom
Prosecution case: 430 pages
More than 200 witnesses
60 lawyers - 51 for the defence, 9 for the prosecution
Trial cost: 1m euros (Ј700,000)
In the shadow of Outreau
In Thursday's hearing, the accused were asked to stand in turn and give their age, profession and home address.
The court is also expected to rule on a request for the proceedings to be heard behind closed doors.
The victims are not expected to appear in court - their testimony has been videotaped.
The evidence being presented in court suggests a cycle of abuse down the generations, our correspondent says.
The couple at the centre of the trial were themselves both sexually abused as children.
They in turn allegedly raped and abused their own children, and allowed family members, neighbours and friends to do the same.
Almost all the defendants come from deeply deprived backgrounds; few have jobs or training. Some are illiterate and almost all lived in the same rundown council estate on welfare benefits.
The prosecution says most crimes were perpetrated in the flat of a former convicted sex offender and in sheds on garden allotments.
"Parents of one kid sold her for a new car tyre," said lawyer Philippe Cosnard, quoted by the AFP news agency. Other children were allegedly bartered for small sums of money, food or cigarettes.
A girl of 10 was allegedly raped by more than 30 adults.
The alleged crimes reportedly came to light when investigators monitored the activities of another convicted sex offender released in 1999. The two men are said to have run the paedophile ring.
The crimes allegedly took place between January 1999 and February 2002 in Angers' Saint-Leonard district.
Prosecutors say about half of the accused have admitted their guilt.
But the prosecution hopes to avoid any repetition of the errors that plagued a previous high-profile paedophile trial - the Outreau case in northern France last year.
In that case, the accused spent months in prison awaiting trial and 13 people were implicated on the testimony of a woman who later admitted she had been lying.