NEW YORK, JUNE 11 -- Former stock speculator Ivan F. Boesky received relatively favorable treatment from federal prosecutors while negotiating the landmark plea bargain agreement that turned him into a cooperating witness in the Wall Street corruption probe, documents released this week show.

During intensive negotiations with the government last September, Boesky's lawyers were able to extract a number of detailed concessions not granted to other Wall Street executives who later made their own plea bargain agreements with prosecutors, according to written agreements released by the government.

Boesky pleaded guilty in April to a single count of securities law violations, carrying a maximum five year prison term. Last November, he paid the Securities and Exchange Commission a record $100 million to settle insider stock trading charges. Two other Wall Street executives implicated by Boesky, Martin A. Siegel and Boyd L. Jefferies, have pleaded guilty to crimes carrying a maximum sentence of 10 years in prison -- twice Boesky's exposure.

Manhattan U.S. Attorney Rudolph W. Giuliani, who supervised the criminal plea bargain agreements, said in an interview today that the different treatment afforded Boesky "in essence indicates the value of cooperating quickly and early rather than waiting to be caught before you cooperate." Giuliani emphasized the breadth and importance of information provided by Boesky as a factor in the negotiations.

Some of the concessions obtained by Boesky's lawyers during the plea bargain talks last fall remain of potential significance.

For example, Boesky is vulnerable to further prosecution for violating his plea agreement only if he "intentionally" fails to provide truthful information to government investigators. And if the government decides that Boesky has broken his deal, it must give advance notice to his lawyers and allow them an opportunity to respond.

Such written protections were not provided to Siegel and Jefferies. They are vulnerable to further prosecution if they break their agreement in any way, whether intentionally or not. And prosecutors are not required to give them notice if they decide the defendants are in violation.

Giuliani said today that he would only bring new charges against any defendant if he was convinced that a plea bargain agreement had been violated intentionally, but he acknowledged that the language in Boesky's agreement is relatively favorable.

In addition, Boesky's deal provides that if he honors his agreement, no information he gives the government will be used against him "in any other criminal prosecution." But the Jefferies and Siegel agreements use much softer language. The two defendants are protected only from further prosecution by the Manhattan U.S. Attorney.

Moreover, Siegel was required to assure the government in writing that he "does not and has not had any foreign brokerage or bank accounts in his name or under his control." Boesky was not required to make that representation to the Manhattan U.S. Attorney or the SEC.

"We were in the nice position of being able to assure the government that there were no foreign bank accounts," said Jed S. Rakoff, Siegel's attorney. "They just wanted that assurance in writing." Otherwise, Rakoff said, the deal he signed with prosecutors was "the standard form agreement."

A special feature of Boesky's deal is his protection from indictment by federal prosecutors outside New York. Whereas Jefferies and Siegel made their deals only with Giuliani, Boesky's agreement was endorsed at Giuliani's request by U.S. Attorneys Joseph E. DiGenova and Robert C. Bonner in Washington and Los Angeles, respectively.

Boesky's lawyers sought those endorsements because the crime to which Boesky pleaded guilty allegedly occurred in New York, Washington and Los Angeles, according to people familiar with the case.

While trading stocks in New York, Boesky said he filed false documents with the SEC in Washington. He also has told investigators that the documents were false because they failed to disclose a secret arrangement between Boesky and Michael Milken, a Drexel Burnham Lambert Inc. executive who works in Beverly Hills, Calif., according to people familiar with the case. Beverly Hills is within the jurisdiction of the Los Angeles U.S. Attorney.

Assets belonging to Boesky's wife and children also are protected in his plea agreement, even if those assets were enriched by Boesky's illegal stock trading.

Giuliani today defended Boesky's treatment. "We wanted to come up with a group of conditions that in essence sent two messages: if you commit crimes like this, you have to be punished, but if you come in early you can mitigate the consequences that you face."