The European Commission has fined four car glass firms a total of more than 1.3bn euros ($1.6bn; £1bn) for running a cartel - its largest such fine.
The four companies are France's Saint-Gobain, the UK's Pilkington, Japan's Asahi, and Belgium's Soliver.
Brussels said the companies colluded over prices, market share and customer allocation between 1998 to 2003.
Competition Commissioner Neelie Kroes said she would not tolerate "such illegal behaviour".
"Management and shareholders of companies that damage consumers and European industry by running cartels must learn their lessons the hard way - if you cheat, you will get a heavy fine," said Ms Kroes.
Saint-Gobain has been fined 896m euros, which amounts to the largest anti-cartel fine ever imposed on a single firm.
The commission said Saint-Gobain's fine was so high as it was a repeat offender, having previously been fined for cartel activities in 1984 and 1988.
Pilkington will pay 370m euros, Asahi 113m euros, and Soliver 4.4m euros.
The four firms controlled 90% of glass for the European car industry between 1998 and 2003.
According to the EC's judgement they discussed target prices, market sharing and customer allocation, in what amounted to "market distortion".
Saint-Gobain said it would immediately appeal the "excessive and disproportionate" fine.
The investigation was triggered by an anonymous tipoff.