A wave of lawsuits is descending on Bear Stearns Cos. and its new buyer, JPMorgan Chase & Co., even as Wall Street struggles to come to terms with the collapse of one of its leading investment banks.

The first known shareholder lawsuit over the implosion of Bear Stearns was filed yesterday afternoon in federal court in New York. Many more such cases are expected. The company already faces suits over hedge funds it ran and could face new claims over its business dealings in recent weeks as well as the negotiations that led to the agreement to sell to JPMorgan for a paltry $2 a share.

“It’s going to be a lot of litigation,” a lawyer who brings class action securities suits, Salvatore Graziano of Bernstein Litowitz Berger & Grossman in Manhattan, said. “We spent the whole day getting phone calls from investors. … It’s a mess, you know?”

Contesting and resolving the expected litigation could cost billions of dollars and is almost certain to dwarf the $236 million JPMorgan plans to pay for Bear Stearns’s stock.

“We’ll be working over the coming months to … sharpen our pencils around transaction-related costs,” JPMorgan’s CFO, Michael Kavanaugh, told reporters and analysts on a conference call Sunday night. “We are working in our minds with something in the $5 to $6 billion pre-tax range … that includes litigation reserves.”

Mr. Kavanuagh did not break out an estimate specifically for litigation, but lumped that number in with the costs of reducing Bear Stearns’s debt and of personnel reductions triggered by the buyout.

“If you want the company, you have to also buy the litigation,” a professor of securities law at Stanford Law School, Joseph Grundfest, said. “It’s like the dowry that goes with the bride.”

The decline of $19 billion in Bear Stearns’s market capitalization since January 2007 is one gauge of the potential losses investors may try to recoup.

A San Diego-based law firm, Coughlin Stoia Geller Rudman Robbins, filed a suit Monday alleging that Bear Stearns and its leaders made false statements about the firm’s financial condition and failed to disclose information investors needed to know to evaluate the company’s value.

Bear Stearns announced on Sunday that it had agreed to be acquired by JPMorgan at a price of $2 a share, down from $30 on Friday and almost $160 10 months ago. The initial drop in Bear Stearns’s price was due to the company’s exposure to securities backed by complex mortgage instruments.

However, last week other banks and investors lost confidence in Bear Stearns’s ability to remain liquid, prompting JPMorgan to propose a takeover under pressure from the Federal Reserve Bank and the Treasury Department.

Under federal securities laws, the investor exposed to the largest loss as the result of an alleged securities fraud is usually entitled to serve as lead plaintiff and to select a law firm to prosecute the suit.

The largest individual investor in Bear Stearns is believed to be a British businessman, Joseph Lewis, who held 11 million shares and may have lost more than $1 billion. A Texas-based investment firm, Barrow, Hanley Mewhinney & Strauss, had a slightly larger number of shares and likely a similar loss.

Vanguard’s Windsor II fund, managed by Barrow, had about 8 million Bear Stearns shares as of year-end.

Coughlin Stoia’s suit seeks certification for a class action on behalf of purchasers of Bear Stearns common stock between December 14, 2006, and March 14, 2008. The lawsuit names as defendants Bear Stearns, the company’s chairman, James Cayne, its president, Alan Schwartz, a director and co-president who resigned last year, Warren Spector, the chief operating officer, Samuel Molinaro, and the chairman of the executive committee, Alan Greenberg.

A lawyer who prepared the suit, David Rosenfeld, said it was possible the officers would be held individually liable. “It definitely happens, more so now than in the past,” he said. Mr. Rosenfeld said it was unclear whether JPMorgan had agreed to indemnify Bear Stearns officers and to what extent so-called directors & officers insurance would cover stockholders’ claims.

The quickly filed lawsuit amounts to an invitation to the largest shareholders in Bear Stearns to join in litigation against the investment firm. However, in recent years, a growing number of large investors have decided to opt out of class action lawsuits and have often secured much more lucrative settlements than those offered to small-time investors.

“Often, these cases are led by relatively small shareholders,” a prominent class action litigator, Herbert Milstein, of Cohen Milstein Hausfeld & Toll, said. He said those who have lost a billion dollars, like Mr. Lewis, often have little incentive to join with others. “He might be interested in doing something on his own. With a claim of that size you can certainly justify that,” the attorney said.

While litigation over the financial collapses at Enron and Worldcom cost banks and investment advisers billions, most outside advisers to Bear Stearns are likely to escape liability this time because in January the Supreme Court ruled, 5-3, that such advisers are generally immune from shareholder lawsuits.

As a group, Bear Stearns employees own an estimated one third of the company, making them the largest shareholder group. However, attorneys said their losses, mostly involving retirement and so-called ESOP plans, would likely be pursued separately from any large class action case.