His wife is being tried at the same time, accused of helping him lure his victims.
Michel Fourniret, 65, is charged with kidnapping, rape and murder in the crimes committed in France and Belgium between 1987 and 2003. The victims, aged from 12 to 21, were strangled, shot or stabbed with a screwdriver.
It is one of the biggest serial killing cases ever tried in France, and drew comparisons with Belgium's notorious pedophile Marc Dutroux, sentenced to life in prison in 2004 for a series of child kidnappings, rapes and murders.
Fourniret appeared in a glass-enclosed defendants' box alongside his wife, Monique Olivier, 59, who is accused of carrying out one of the murders along with her husband, and of complicity in several others. Prosecutors say she helped him track down virgins for him to rape and kill. Both face life in prison if convicted.
Fourniret struck a defiant pose on day one of the trial. When the judge asked him to identify himself, he held up a piece of paper with the words "Without a closed courtroom, staying tightlipped."
The judge did not appear to respond.
Fourniret also passed to the judge a rolled paper tied in a red ribbon, which his lawyer said was a message to the victims' families. He asked that the judge read it, and the judge declined.
Defense lawyer Pierre Blocquaux told the court Fourniret did not want to be defended by him or his two other lawyers.
Olivier appeared to be cooperating and answered the judge's opening questions about her identity. She looked for a long time at the families and did not react as crowds of photographers snapped her image as she entered.
Her lawyer, Jacques Delandes, said she planned to apologize to the victims' families.
Jean-Maurice Arnould, lawyer for the family of slain 12-year-old Elisabeth Brichet, said the family was not expecting an apology from Fourniret.
"He's a man without conscience," he said.
Elisabeth's father said he did not want to hear Fourniret's account of his daughter's murder.
"We don't want new facts of the crimes; for us it's already hardly bearable," Francis Brichet told The Associated Press. The child's body was found along with that of 21-year-old Jeanne-Marie Desramault in the wooded grounds of Fourniret's former property in northern France.
An array of exhibits sat in the courtroom including a shotgun, two revolvers, a screwdriver and various pieces of rope.
Belgian police detained him in June 2003 after his bungled kidnapping of a 13-year-old girl. The girl gave authorities his license plate number after she managed to unbind her hands and escape from the back of Fourniret's van.
Belgium extradited Olivier to France in 2005 and Fourniret in 2006. Judicial officials in both countries decided the case should be tried in France because six of victims were French citizens.
Investigators suspect Fourniret may also have been involved in several other murders, as well.
Hundreds of reporters attended the proceedings, which were broadcast on three screens inside the courthouse.