THOUGH THE ORIENTE is clearly a disaster area, the scientific data is far from cut and dried, and Chevron denies almost every allegation that fell into its lap after its merger with Texaco.

In Quito, I interviewed Rodrigo Perez, the Chevron subsidiary's chief legal adviser in Ecuador. Perez began working for Texaco in 1969, when he was a young man; he's 69 now, with the comforting manner of a family doctor. The case has taken its toll. "I am tired," Perez confessed during my 2005 visit. "I would love to go to the beach for a month or two and write."

But the attacks have been relentless, and Perez wearily outlined Texaco's position, as he's done for years. Any damage caused by the company was not nearly as severe as the suit charges, he said. Even so, dumping wastewater was "common practice" in the bygone days of oil extraction, which means Texaco wasn't doing anything out of the ordinary. "If you filter it first," Perez said, "in 200 meters you don't have any way of knowing the water was dumped, because those are big rivers." Poverty and the continuing operations of state-owned Petroecuador—a notorious polluter responsible for 117 spills in the first half of 2006 alone—are the real source of pollution and disease, the company insists. And the patchwork of medical studies don't prove higher incidences of disease that can be traced, absolutely, to Texaco's activities.

To get a firsthand look, I visited San Carlos and spoke with Oscar Ojeda, a doctor at the clinic there. He said the village has recorded what seems like an inordinate number of cancer cases, including leukemia, and he believes oil pollution is the cause. Throughout San Carlos, I smelled petroleum in the air, and Ojeda said he would never drink the water or swim in the rivers, as most local people continue to do. But even if a link could be proved between the village's cancer rate and pollution, the legal and scientific question remains: Were the cancers caused by Texaco before 1992, or by Petroecuador in the years since?

Chevron has a second line of defense: In the mid-1990s, Texaco paid $40 million to remediate some sites in the Oriente; in keeping with the roughly 30-70 management split between the companies, Petroecuador would be responsible for remediating the others (which it hasn't done). In return, in 1998, Ecuador's government indemnified Texaco from further claims.

Donziger describes this cleanup as a fraud, alleging, for example, that Texaco merely poured dirt over waste pits rather than removing the waste and subsoil. In his always-turn-it-up-a-notch style, he helped persuade the Ecuadorean government to open an investigation into the remediation, adding new fire to a separate case. In a New York federal court, Chevron is seeking assurances from the Ecuadorean government, stemming from the indemnification, that Petroecuador will pay any damages awarded in Lago Agrio. That trial is scheduled to begin in March.

Though it stretches the imagination to think of Chevron as an innocent party, the company is clearly not the only possible culprit. Texaco operated most of the wells in the Oriente until 1992, but other American companies were present, such as Occidental Petroleum and Maxus Energy, though their operations were generally regarded as cleaner than Texaco's. Pollution has not ceased since Texaco departed, thanks to the negligence of Petroecuador and a government in Quito that doesn't fully enforce its own regulations. Furthermore, oil pollution isn't the sole problem. Today, deforestation in the Oriente is so extensive that I could barely imagine, as I drove around, that the region was untouched rainforest only a few decades ago. Vast environmental crimes have certainly occurred, but who's to blame? Chevron suggests looking elsewhere.

"Despite Petroecuador's clear acknowledgement of responsibility and the substantial evidence of the company's poor environmental record," Chris Gidez wrote me in an e-mail, "plaintiff's attorneys continue to solely target Chevron not because it is the proper target, but because it is the most convenient one and has the deepest pockets."

Justice is rarely blind in Ecuador. Until recently, verdicts would never have favored the little guy with a grudge against well-connected gringos. But the nation's newly elected president, Rafael Correa, joins Venezuela's Hugo Chávez and other ideological soul mates in Bolivia, Nicaragua, Brazil, Argentina, Peru, and Chile. In Venezuela, Chávez has forced foreign oil companies to rewrite their joint-venture contracts, while Bolivia has just nationalized its oil-and-gas industry. In Ecuador, even before Correa was elected, the government imposed a windfall tax on foreign oil companies and terminated Occidental Petroleum's lucrative exploration contract.

Most Ecuadoreans never visit the Oriente or Lago Agrio, which is regarded as a kind of lawless Love Canal. But frequent coverage in Quito's newspapers has generated national interest in the case. An adviser for Chevron—who tracks public opinion in Ecuador and who asked to remain anonymous—told me that if the judge issues a verdict against the company, he'll be treated as a hero. This adviser was exaggerating, but only somewhat, when he added that any judge ruling for Chevron would be "carried out on his back"—in a coffin.