Millions of euros claimed in damages for a German firm that gave defective breast implants.
TUV Rheinland had certified that implants made by Poly Implant Prothese (PIP) conformed to European safety rules, but the French firm shut in 2010 after it was found to have used substandard, industrial-grade silicone gel that caused abnormally high implant rupture rates.
More than 400,000 women around the world are thought to have received implants made by PIP.
TUV Rheinland is being sued by six PIP distributors from Bulgaria, Brazil, Italy, Syria, Mexico and Romania for 28 million euros ($36 million).
In addition, more than 16,000 women with PIP implants are suing the firm for 16,000 euros in damages each. They are mainly from South America.
Experts disagree over the potential health risks involved, and as the trial opened in a court in the southern French city of Toulon, the prosecution and defence squabbled over whether the court had the jurisdiction to hear the case.
Lawyers for TUV said the trial should be held in Germany or Paris -- where TUV Rheinland France is based -- or in the countries of the women filing suits and questioned the credibility of the women involved.
"What is the proof that they really have PIP implants?" said TUV lawyer Cecile Derycke.
The substandard gel was in 75 percent of PIP breast implants, saving the company about one million euros ($1.3 million) annually, according to an ex-company executive.