Firm co-founder Melvyn Weiss entered his pleas through his lawyer to two counts of conspiracy and one count each of obstruction of justice and making false statements in relation to documents that were the subject of a grand jury subpoena.
Not guilty pleas were also entered by plaintiff Seymour M. Lazar, who did not attend the hearing and was represented by his attorney, and lawyer Paul Selzer, who appeared in court, to charges contained in a superseding indictment filed last month.
Lazar, who allegedly received kickbacks, and Selzer are each charged with four counts of money laundering. Selzer also is charged with one count of conspiracy to launder money.
Prosecutors said the firm previously known as Milberg Weiss Bershad & Schulman made an estimated $250 million by filing class-action lawsuits against some of America's largest corporations. Kickbacks were allegedly paid to people who agreed to be plaintiffs.
The firm also has been charged in the case and pleaded not guilty Monday to one count each of conspiracy, mail fraud, money laundering and obstruction of justice in the superseding indictment.
The seven-year investigation has resulted in guilty pleas by several former partners and lawyers at the firm.
If convicted of all four counts, Weiss faces a maximum sentence of 40 years in prison. He remained free after posting a $1.5 million bond on Friday.
Weiss, 72, surrendered his passport and was allowed to travel without conditions to California, New York, Washington, D.C., and Florida, where he has a second home.
If Weiss travels elsewhere in the United States, he must inform court officials if he intends to remain there more than 72 hours.
Last week, former partner Steven Schulman, 56, pleaded guilty to a racketeering conspiracy charge. He agreed to forfeit $1.85 million to the government and to pay a $250,000 fine.
Sentencing was scheduled for June 23 when Schulman could face up to 20 years in prison.
In addition, prosecutors have said William S. Lerach, a former top attorney with the firm, now known as Milberg Weiss, agreed to plead guilty to conspiring to obstruct justice and making false statements under oath.
Lerach, who is awaiting arraignment, will forfeit $7.75 million to the government, pay a $250,000 fine and accept a sentence ranging from one year to two years in federal prison, prosecutors said.
He resigned last month from the firm he founded in San Diego, now known as Coughlin Stoia Geller Rudman & Robbins.
Former Milberg Weiss Bershad & Schulman partner David Bershad also has pleaded guilty to conspiracy and agreed to cooperate with the government. He will be sentenced early next year.
The firm co-founded by Weiss has sued some of the nation's largest companies, including Lucent, Microsoft and AT&T.
He and top lawyers dominated the industry in securities class-action lawsuits, which involves shareholders who claim they suffered losses because executives misled them about a company's financial condition.
Prosecutors believe the firm, which also has been indicted, enlisted people to take part in more than 225 class-action and shareholder lawsuits by secretly paying them millions of dollars in kickbacks.
In doing so, it allowed Milberg Weiss attorneys to be among the first to file litigation and secure the lucrative position as lead plaintiffs' counsel.