NEW YORK, DEC. 18 -- Ivan F. Boesky, the speculator who generated the biggest stock trading scandal in Wall Street history and sparked financial corruption investigations from London to California, was sentenced today to three years in prison.

In a packed Manhattan courtroom, a thin and pensive Boesky stood silently as Judge Morris E. Lasker pronounced the sentence just after 10:30 a.m. Boesky had faced a maximum five-year prison term after pleading guilty to one criminal charge of filing false documents with the government.

Reaction to the sentence from defense lawyers, prosecutors and others was generally favorable, although some remained critical of the plea bargain with the government that limited Boesky's possible sentence to five years.

Lasker emphasized that the three-year sentence took into account both the enormity of Boesky's crimes and the "unprecedented" extent of his cooperation, which included tape recording conversations implicating some of Boesky's highly placed former Wall Street associates.

"There is no doubt that Boesky has been humiliated, vilified and cut down to size {to} a degree rarely heard of in the life of a person who was once regarded favorably as a celebrity," Lasker said.

A prison sentence was necessary, however, because "the public has come to regard this proceeding as the ultimate representation of the insider trading scandal," Lasker continued. " ... Ivan Boesky's offense cannot go unpunished. Its scope was too great, its influence too profound, its seriousness too substantial merely to forgive and forget."

In a 45-minute plea for leniency, Leon Silverman, one of Boesky's attorneys, said his client should receive a shorter prison term than the two-year sentence given to former Drexel Burnham Lambert Inc. investment banker Dennis B. Levine last February.

Levine was charged with making about $12.6 million in illegal profits by trading stocks on the basis of confidential information about upcoming corporate takeovers.

Silverman said Boesky deserved a shorter sentence than Levine because his cooperation was far more valuable to the government.

Silverman lamented that Boesky has been ostracized because of his cooperation, labeled a "stool pigeon" and a "traitor."

"There is indeed a blood lust in the community," Silverman said.

Boesky also paid the government $100 million to settle insider trading charges.

Lasker, however, said Boesky's crimes were so extensive they indicated a "systemic problem in the financial market."

Boesky, who profited as an arbitrageur by trading stocks of companies involved in corporate takeovers, was implicated by Levine.

Levine revealed to government investigators last year that he and Boesky had entered into an illegal profit-sharing arrangement based on swapping inside information about takeovers.

Boesky's cooperation with the government's continuing investigation of Wall Street corruption has led to guilty pleas by former investment banker Martin A. Siegel and former brokerage chief Boyd L. Jefferies.

Boesky disclosed that he had agreed to pay Siegel about $700,000 in cash in return for inside information about corporate takeovers; Boesky also told authorities that he and Jefferies violated securities laws through a stock "parking" arrangement -- moving shares back and forth between them and producing phony documents to conceal true ownership.

Boesky's cooperation has sparked investigations of other firms and prompted numerous charges in a British stock trading scandal.

Sources said today that government probes of Drexel Burnham Lambert Inc.; Jamie Securities; Seligmann, Harris & Co., and two other brokerage firms are continuing.

While Boesky is due to begin serving his three-year prison sentence in March, U.S. Attorney Rudolph W. Giuliani said the former speculator" ... Ivan Boesky's offense cannot go unpunished. Its scope was too great, its influence too profound, its seriousness too substantial merely to forgive and forget." Judge Morris E. Lasker will remain available to aid the government in its investigations.

Boesky's cooperation could include appearances as a witness at future trials.

Giuliani said that under federal regulations, the 50-year-old Boesky would be eligible for parole after serving about one year, adding that he would likely serve no more than two years.

The longest sentence ever given in an insider trading case was the four years imposed on former deputy Defense secretary Paul Thayer in 1985 for passing on confidential information about takeovers.

Today's sentencing was an ignoble end to Boesky's dramatic rise and fall on Wall Street.

The son of a Detroit delicatessen owner, Boesky married a wealthy heiress in 1962.

After attending law school at the Detroit College of Law and working briefly as a law clerk, Boesky was unable to land a job with a local law firm. He moved with his wife to New York in 1966, but again had difficulty starting a career.

While working at several small Wall Street firms, Boesky began to specialize in arbitrage, eventually focusing on merger arbitrage by aggressively trading the stocks of companies involved in corporate takeovers.

Eager to prove himself and hungry to make a fortune, Boesky launched his own firm in 1975. He was known on Wall Street for working 18- to 20-hour days, rarely sleeping and routinely taking huge and risky trading positions.

Before Boesky came along, arbitrage was a little-known specialty. But Boesky's desire to raise capital and build a reputation for excellence led him to seek considerable publicity.

While he was regarded by some on Wall Street as an uncouth outsider, earning him the nickname "Piggy," Boesky courted the press and made speeches across the country. His fame and fortune grew side by side; by 1986, Boesky's arbitrage partnership owned nearly $3 billion in stocks and employed about 100 people.

Boesky wrote a book describing the art of arbitrage, arguing that financial analysis and hard work were the secrets of his fortune. A father of four children, Boesky was also lauded for giving generously to charities.

In the end, with more and more capital to invest and his reputation for performance at stake, Boesky was not content merely to analyze and speculate.

Beginning at least as early as 1982, after suffering heavy trading losses, he began to seek out inside information about upcoming deals, setting the stage for his eventual disgrace.

When asked by Judge Lasker if he had anything to say at his sentencing, the once voluble Boesky rose and, speaking in a soft voice, referred to his remarks at an earlier sentence hearing.

"I expressed my profound sentiments to you on the date we met and I could not make it more deeply now," Boesky said. Boesky had told Lasker earlier, "I am deeply ashamed and I do not understand my behavior."

"If he was an arrogant man before, his arrogance has now been stripped away from him," said Assistant U.S. Attorney John Carroll, who spoke for the government at today's sentencing.

After his sentencing, Boesky walked down the front steps of the federal courthouse, where police had erected barricades to hold back the crowd.

He and his security guards entered a waiting car, which struggled to pull away from the mass of reporters and cameramen. Stopping briefly at a traffic light in front of the courthouse, the car carrying Boesky ran a red light and headed uptown.