The Indians told a federal court that for years, the oil giant dumped highly toxic water, a by-product of oil drilling, directly into Ecuador's rain forest.
"What Texaco gave us is a disaster," a tribal leader said in Spanish. "They've done away with our rivers, our forests, our animals."
The Indians say that anywhere else in the world, Texaco puts that poisonous water back into the oil well.
"If you go to Kuwait, or Texas, you never see this," says Cristobal Bonifaz, the attorney representing the tribes. "All you see is the water disappear."
Texaco, which left Ecuador in 1992, admits it dumped toxic water, but says it was legal in Ecuador. In fact, the government of Ecuador now owns the wells, and it's still dumping today.
"The company acted responsibly in full compliance with all laws and regulationsÂ…this matter belongs in Ecuador," says Texaco spokesman Chris Gidez.
The controversy in the case is not whether Texaco damaged the rain forest, but whether the Indians should be allowed to use American law to sue Texaco in an American court.
The Indians claim the contamination was so vast, it violated their human rights, and only American courts can make Texaco pay.
"This is where Texaco profits, this is where the shareholders made money, from this rain forest exploitation," Bonifaz says.
Big business is watching. If the tribes can sue, any U.S. corporation operating legally overseas could be sued under U.S. standards at home.
"It could include all kinds of things beyond environmental, human rights, fraud, any kind of claim anybody can think of," says Quentin Riegel of the Association of Manufactures.
If the judge dismisses the case, the Indians say Texaco walks away from this environmental ruin. But taking the case would be a step toward making America courtroom to the world.