The case, dubbed the "Carlton Affair" after the luxury hotel in the northern city of Lille where authorities say the prostitution network was based, has riveted France and stirred debate about the extent to which the personal lives of public figures should remain private.
Paying for sex is not illegal in France, but it is against the law to procure prostitutes for others or to run a prostitution business.
Strauss-Kahn, 65, has admitted attending "libertine" parties in Paris, Brussels and Washington between 2009 and 2011, when he was serving as IMF chief, according to French news reports. But he says he did not know that some of the women present were prostitutes.
"As you can imagine, at these kinds of parties you're not always dressed, and I challenge you to distinguish a naked prostitute from any other naked woman," his attorney, Henri Leclerc, told reporters after the investigation was launched in 2011.
Prosecutors had recommended dropping the charges against Strauss-Kahn on grounds of insufficient evidence, but the judges who ordered the trial in Lille said he must have known that the women were paid, as the parties were organized on his behalf.
Participants quoted in court documents described scenes of "carnage" and said Strauss-Kahn was the "king of the party," according to a report in the French weekly Le Journal du Dimanche. [Link in French]
If convicted, Strauss-Kahn could face up to 10 years in prison and fines totaling $1.7 million. He is accused with 13 others, including a police commissioner, high-flying businessmen and the owner of a chain of sex clubs who is known as "Dodo the Pimp."
The trial, which is scheduled to last three weeks, has been described as a test of changing attitudes in France about the seamier side of politicians' personal lives.
Strauss-Kahn's defenders contend that he is the victim of a feminist-inspired moral crusade in a country that has long poked fun at Anglo-Saxon "puritanism." His critics argue that he has a history of predatory behavior toward women.
Strauss-Kahn was forced to resign as IMF chief when he was arrested in May 2011 and accused of sexually assaulting Nafissatou Diallo, a housekeeper at the Sofitel Hotel in New York.
He claimed that the sex was consensual and involved no violence. The criminal charges against him were eventually dropped over concerns about Diallo's credibility, and he reached a settlement in a civil suit brought by his accuser.
French prosecutors in 2011 also dismissed a French writer's claim that Strauss-Kahn had tried to rape her during an interview in 2003. Officials said the statute of limitations for pursuing the case had passed.
Strauss-Kahn is not expected to testify in the latest case until next week.