It is billed as one of the country's biggest criminal trials, and the largest paedophile trial held in France.
The case is one of the largest criminal trials France has seen
In total, 66 men and women face charges of rape and child sex abuse on 45 children, some of them their own.
The abuse is alleged to have taken place over three years between 1999 and 2002 in the western town of Angers.
The case initially came to the attention of the authorities at the end of 2000, after a teenage girl accused two members of her family of raping her.
But a judicial investigation into charges of rapes and pimping was not formally launched until February 2002.
Three people were placed under formal investigation - a step short of being charged - at the end of that month.
In April last year, the initial phase of the investigation was completed and 72 people were placed under investigation.
Six were released without charge, but 66 remained under investigation, including 39 who are in custody on charges of rape and pimping.
The other 27 face lesser charges of sex abuse and failure to report a crime.
However, observers say there is very little information available on the initial stages of the investigation prior to February 2002.
This is something the trial should shed some light on, says Le Monde newspaper.
Already very high profile, this trial will be watched particularly closely, coming as it does only a few months after another high-profile child abuse case - that of Outreau in northern France, which collapsed spectacularly last summer.
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 (£700,000)
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. One suspect committed suicide while in detention.
The case was also based in large part on the accusations of the 18 children who said they had been abused.
In the event, the trial which was thought to have been that of a wide paedophile ring ended in the conviction of a handful of people.
This time around, prosecutors and lawyers say they are confident the case has been well investigated.
"This is not the trial of the investigation, which was very correctly conducted, but it is a one-way investigation," says defence lawyer Patrick Rouiller.
"It was about identifying the aggressors, full stop. Without looking into the deficiencies of the judicial follow-up or of social services," he told Le Monde newspaper.
Although many of the men and women accused were being monitored by the social services, those services say they did not notice anything.
More than half of the accused have admitted their guilt, but there is said to be very little material evidence against them.
Earlier this year, Justice Minister Dominique Perben announced a reform of the justice system in the wake of the Outreau debacle.
The reform will focus on penal procedures as well as the use of experts, who were given a prominent role in Outreau, in child abuse cases.
Mr Perben says he is also considering a revision of testimony procedures for children who say they are victims.
In spite of all the precautions, some doubt justice will be done in this case.
"We are certain of not having identified all the victims and it is probable that we have not identified all the aggressors," deputy public prosecutor Herve Lollic told the AFP news agency.
The second phase of the investigation to determine the extent of the alleged paedophile ring is still ongoing.