Bernie Ebbers, former chief executive of bankrupt phone company Worldcom, has pleaded not guilty to charges of orchestrating an accounting fraud.
Mr Ebbers has always denied any wrongdoing
At a US District Court in Manhattan he denied three charges of fraud, conspiracy and making false statements.
Earlier in the day he had surrendered to FBI offices in New York.
On Tuesday US Attorney General John Ashcroft alleged Mr Ebbers was behind Worldcom's "illegal scheme", which saw it crash with $11bn (£5.93bn) debts.
Mr Ebbers, who turned himself in at the Jacob K Javitz Federal building in Manhattan, built Worldcom into the US's second-largest long-distance phone carrier.
His lawyer, Reid Weingarten, had earlier said his client would clear his name at trial.
"Bernie Ebbers never sought to mislead investors, never
sought to improperly manipulate Worldcom's numbers, never improperly took any money and never sought to hurt the company he built," he said.
He is charged with fraud, conspiracy to commit securities fraud, and filing misleading data with the Securities and Exchange Commission (SEC).
Former finance chief Scott Sullivan is due in court in April
It is alleged Worldcom, now called MCI, used accounting tricks to conceal a deteriorating financial condition and to inflate profits.
Mr Ashcroft said Mr Ebbers had been behind the filing of reports that did not reveal the true position of Worldcom's finances.
And he said that Mr Ebbers and his co-conspirators had engaged in "an illegal scheme" to mislead the investing public, shareholders, analysts and the SEC.
On Tuesday former chief finance officer Scott Sullivan admitted charges of conspiracy, fraud and making false statements about Worldcom's financial health to regulators.
The finance boss, due to go on trial in April, had previously denied charges he orchestrated the accounting fraud that improperly recorded capital expenses and masked net losses.
The 42-year-old was fired from the company in June 2002, and it is thought he will be a major factor in any case against Mr Ebbers.
Mr Ebbers resigned from Worldcom under pressure in April 2002.