Enron founder Kenneth Lay

Jeffrey Skilling became president and chief operating officer of Enron in January 1997.

The two presided over the spectacular collapse of the energy giant in 2001 and were also accused of lying to investors about its financial problems.

The two former chief executives faced 34 counts relating to Enron's collapse.

The energy trading firm went from being the US's seventh largest company to bankruptcy, amid allegations of accounting irregularities.

In October 2001, it had to announce huge losses as its shares dived.

Two months later, it filed for bankruptcy as allegations began to emerge that it had used off-the-books offshore firms to hide losses.

The firm's auditor, Arthur Andersen, was forced out of business following the collapse of Enron, as it was seen as having colluded in the accounting practices.

In a separate case, Lay has also been found guilty by a District Court judge of four charges of bank fraud totalling $75m.

The two plan to appeal their convictions.

"We fought the good fight," Skilling told reporters outside the court after the verdict.

"Some things work, some things don't. Obviously I am disappointed but that's the way the system works."

USA Inc in the dock

The Enron case is the culmination of a string of high-profile cases involving corporate misbehavior.

Among them was the conviction of Worldcom chief executive Bernie Ebbers for fraud and conspiracy, and homecare queen Martha Stewart for insider trading.

Andrew Fastow, Enron's former chief finance officer, pleaded guilty to his part in the scandal in 2004 having agreed to testify against his former bosses. He paid fines totalling $23 million and received a sentence of 10 years in jail.

Numerous other Enron executives have been convicted - many after pleading guilty - in court cases across the US includng Enron's Chief Trader Tim Belden who was sentenced to 5 years in prison and fines of $13 million.

Blockbuster trial

The trial of Lay and Skilling in Houston follows four years of investigation by the Department of Justice's Enron Task Force. It lasted for 15 weeks, with 54 witness called by the two sides.

The verdict came on the jury's sixth day of deliberations.

Lay has been found guilty of all six fraud and conspiracy charges that he faced.  He faces a maximum of 165 years in prison, and fines of $300 million.

Lay posted a $5 million bond secured with family-owned properties at a hearing following the verdict. He was ordered to stay in the Southern District of Texas or Colorado.

Skilling, 52, was convicted on 19 counts of conspiracy and fraud. Skilling was acquitted of nine other charges relating to insider trading. Combined with his conviction on one count of insider trading, he faces 185 years in prison, and fines of $183 million.

"Obviously, I'm disappointed," Skilling told reporters outside the courthouse. "But that's the way the system works."