One of the fired employees, Clayton Vernon, had asked Kenneth L. Lay, Enron's chairman, during an earlier internal online discussion whether Enron had used aggressive accounting to overstate its profits. It is unclear whether Mr. Vernon's question to Mr. Lay, which came in September, two months before he was dismissed, played any role in his firing. But a coarsely worded message critical of Mr. Lay that Mr. Vernon posted in November under a screen alias was traced back to him in less than a day.

The second fired employee, according to Enron, was the person who revealed in early December on the Internet that Enron had paid $55 million in retention bonuses to top managers and executives just before it filed for bankruptcy protection and laid off 4,000 workers on Dec. 2. The bonuses were sharply criticized by Enron employees, many of whom had their retirement savings wiped out by Enron's collapse. Enron declined to identify the second fired employee.

Enron also declined to comment on any other details of the two firings, and it would not say whether it had dismissed any other employees because of Internet postings. Mr. Vernon confirmed that he had been fired for postings that the company viewed as offensive.

"We're not going to discuss internal security actions," said Mark Palmer, a spokesman for Enron. "But we will say that we will protect very vigorously the corporation's property."

Both firings involved material posted in an online forum about Enron on Yahoo (news/quote), whose message boards are among the most heavily used on the Internet.

It was not clear how Enron identified the employees behind the postings. People who post messages on Yahoo often believe that they cannot be traced if they do not use their real names. But many companies have the technical means to track the online activities of employees who use company computers and servers.

In addition, Yahoo's privacy policy allows it to disclose personal information about people who post messages that it deems abusive or "invasive of another's privacy, hateful, or racially, ethnically or otherwise objectionable," or that reveals confidential corporate data.

Even so, a Yahoo spokeswoman said Yahoo had not given Enron any information about anyone who posted a message. Despite the disclaimer in its privacy policy, she said, Yahoo generally divulges personal information about users only in response to a court order.

In any case, Enron apparently had little difficulty finding Mr. Vernon, who posted most of his messages from the company's Houston headquarters, where he worked designing computer-based models to estimate the value of Enron's energy trades.

A native of Midland, Tex., who describes himself as a political progressive, Mr. Vernon said that when he joined Enron in December 1999, he hoped that the company would be diverse and a meritocracy.

But in the course of two years working at Enron, he said, he "realized it was just another Houston, Texas, corrupt thing — that we grow in this town — where the rich white Republicans think they can write any law they want to at any time."

His frustration grew, he said, when Mr. Lay took part in an online chat within the company on Sept. 26 and brushed off Mr. Vernon's question about the way Enron had accounted for deals it had made with supposedly independent partnerships. Enron began to collapse after it became known in November that it had used the partnerships to overstate earnings by at least $600 million.

By mid-November, with Enron's stock plunging, Mr. Vernon had begun to post dozens of messages a day on the Yahoo discussion board under the screen name "utlonghornsrule," referring to the University of Texas, where he received a master's degree in economics.

His messages warned investors away from Enron's stock, and many sharply criticized Enron and Mr. Lay. "We were just sitting there with nothing to do," Mr. Vernon said of the period when he posted the messages. "We were just sitting there watching our stocks go down."

The final straw for him came Nov. 19, he said, when Enron canceled its Christmas party. At 5:16 p.m. that day, in a (not always grammatical) message sprinkled with vulgarities, Mr. Vernon wrote that Mr. Lay had "just cancelled the Enron christmas party so he wouldn't have to show up for his own party with armed bodyguards."

He went on, "Lied and said employees were ambivalent. Trust me, nobody believes a word" that Mr. Lay says, the posting said, using a vulgar epithet. "People have enjoyed the company spending a few dollars on them and giving them a chance to laugh and dance a bit. Esp since most of us adore our coworkers.

"Ken Lay is the sorriest sack of garbage I have ever been associated with, a truly evil and satanic figure."

Other people quickly posted responses defending Mr. Lay, including one who wrote, "1) You are an embarrassment to UT — so shut up. 2) You don't know what you are talking about — You don't run with the big dogs." Mr. Vernon said the style of that note led him to think that it was the work of a senior Enron employee.

It did not take long for Enron to find out the identity of "utlonghornsrule." The day after his vituperative posting, Mr. Vernon said, he was called into a meeting with his manager and a top human resources officer. "My boss said, `What were you doing?' and I said, `I was frustrated,' " Mr. Vernon said. "They escorted me out immediately." He said he had been paid his salary, but no severance pay.

Mr. Vernon said he understood why he was fired. "I was using their equipment," he said, "I was in their building, and it was a flagrant violation of company policy to do what I did. I'm not going to litigate it. I don't think it was unfair."

He does not see himself as a whistle-blower, he said, and he is embarrassed by the language his anger led him to use — but he is still angry.