undreds of plaintiffs' lawyers who claim that people were injured or killed by the painkiller Vioxx plan to meet next week to lay the groundwork for a nationwide legal assault against the drug's maker, Merck.

The lawyers expect the discussions to begin informally on Tuesday in Pasadena, Calif., in the hallways of a conference on Vioxx litigation that will also be open to defense lawyers. On Thursday, at a meeting in Las Vegas for plaintiffs' lawyers only, those who are suing Merck, or plan to, expect to discuss specific strategies.

"We can't compete with big pharmaceutical companies by ourselves, but when we get together, we can become formidable," said Daniel E. Becnel Jr., a lawyer in Reserve, La., who has led such organizational efforts in other drug cases and in tobacco litigation. "This is a case that needs to be managed by the premier lawyers in the country."

J. Michael Papantonio, a lawyer in Pensacola, Fla., who organized the Las Vegas meeting, said about 500 plaintiffs' lawyers were expected to attend.

Even before Merck withdrew Vioxx from the market on Sept. 30, citing what it said was new evidence that the drug increased the risk of heart attacks, strokes and other serious ailments, hundreds of patients had filed lawsuits around the country. Since then, countless other lawsuits have been brought - no one yet has an accurate figure - and more are expected.

Merck, which has said it withdrew the drug as soon as it had conclusive evidence of unacceptable risk, declined to discuss its defense strategy.

This week, the incentives to sue have multiplied. The Food and Drug Administration published a report on its Web site on Tuesday by a staff researcher, concluding that more than 27,000 deaths could be attributed to Vioxx based on comparisons with how patients taking other painkillers had fared.

Yesterday, The Lancet, a respected British medical journal, published an analysis of all the clinical trials of Vioxx completed by 2001, and concluded that Merck and the F.D.A. should have known enough about the drug's hazards to withdraw it years ago.

The plaintiffs' lawyers plan to compare notes next week on the types of clients who may make the strongest cases, with a premium on people who were in demonstrably good health before taking Vioxx.

The group also intends to discuss ways to cooperate in gathering evidence and expert testimony, and in devising tactics to influence where the bulk of the cases may end up, as state and federal judges consolidate them. Until such matters are resolved, how soon any of the cases may come to trial is uncertain, including one that had been expected to begin as early as next month in federal court in Birmingham, Ala.

Many lawyers will also be jockeying for roles that will maximize their influence, and ultimately their reimbursement, as the litigation unfolds.

More than 20 million Americans have used Vioxx since it went on the market in 1999. Millions more used the drug overseas. Based on the number of Vioxx customers and the seriousness of the injuries, the Vioxx lawsuits would appear to have the potential to dwarf recent cases like the one against Baycol, a cholesterol-lowering drug used by about 700,000 Americans, and the one against the diet supplement fen-phen, which an estimated six million people took.

Baycol's maker, the Bayer Group of Germany, said in late September that it had paid $1.09 billion to settle 2,861 lawsuits and that 7,577 suits were pending. And Wyeth, the marketer of fen-phen, faces continuing legal battles with plaintiffs who opted out of a settlement program that pays victims from a $3.75 billion trust fund. Wyeth has set aside $16.6 billion to cover its liabilities.

Many plaintiffs' lawyers say it is too early to make a realistic assessment of Merck's financial vulnerability. Merck has long been among the strongest companies financially, with a credit rating among the highest in American business.

In their meetings next week, the lawyers are likely to weigh the potential impact of this week's national elections. There were big gains for Republicans, who have been leading efforts to curb product liability lawsuits. A related concern for the plaintiffs' lawyers is the F.D.A.'s continuing efforts under the Bush administration to persuade judges that F.D.A. approval of a drug, along with warnings on the label, should go a long way toward shielding the maker from lawsuits.

So far, most state judges have rejected the F.D.A. immunity argument. But if courts began to accept it - or if Congress made it the law of the land - plaintiffs' lawyers would have the higher hurdle of arguing that Merck deceived the F.D.A. by hiding or distorting damaging data. That case would be hard to make without supportive testimony from the agency, some lawyers said. The personal injury lawsuits - or tort cases, as lawyers call them - can be filed in state or federal courts and in many cases can name other parties, like doctors or drug distributors, as co-defendants with Merck. In the hundreds of Vioxx lawsuits filed before Merck took the drug off the market, the action was primarily in New Jersey, where Merck is based, and the big states of Texas and California. But the financial burden of taking on a giant like Merck while it continued to insist that Vioxx was safe and effective scared away many lawyers. "It's been a quiet little mass tort for a long time," said Carlene Rhodes Lewis, a Houston lawyer whose firm was among the pioneers when it began filing Vioxx complaints in 2001. Ms. Lewis and her partners took on nearly 300 such cases by the time Merck pulled the plug on Vioxx. Merck's withdrawal of Vioxx has made it much easier for lawyers to argue to a jury that the product should not have been on the market. But proving liability could still be difficult. The data from clinical studies suggest, so far, that the most serious health problems hit patients who had used Vioxx for 18 months or longer. Merck has said it does not know yet how large that group is. In addition, many possible Vioxx victims may find it difficult to pin their health problems on the drug if forced to go to trial, lawyers who filed the early cases said. The injuries linked to Vioxx are also common among people who have not used the drug, and they have many causes. "The person who should never have taken Vioxx and should have been warned by Merck, the person with multiple risks of cardiac problems, may not make the best client, because it may be harder to prove that Vioxx caused the heart attack," said Cynthia Anne Solomon, a lawyer in Mount Pleasant, S.C. As a result, the pioneering plaintiffs' lawyers in the Vioxx litigation have been carefully screening potential clients in search of those who were relatively healthy before they took the drug and suffered injuries. Some of those lawyers said they were worried that lawyers who rushed into the field after Merck withdrew the drug, including law firms soliciting clients with radio and print advertising, would muddy the legal landscape with questionable claims. "For every hundred calls we get, there are only two or three top-end cases," Mr. Papantonio said. He and others said that Merck, if it follows the course of other drug companies in similar situations, is likely to try to settle the strongest cases against it and fight some of the weaker claims in trials. If it wins those trials, it could knock down the settlement value of the vast majority of claims against it and cut billions of dollars from its potential exposure. Merck recently asked the panel of judges that supervises the way mass torts are handled in federal courts to assign all of the lawsuits to one judge. Mr. Becnel filed a similar petition. The panel is expected to hear arguments on the petitions and where the cases should be consolidated at its January meeting. Many lawyers involved in the lawsuits say the federal consolidation process should hasten final settlement of most of the Vioxx cases. The state cases in New Jersey and California have already gone through such a process. But the effort to centralize the federal cases while sorting out which cases will remain in state courts - where plaintiffs' lawyers usually prefer them - could very likely lead to procedural battles that may delay the first Vioxx trials. Several were on course to begin in the next few months. "It's up in the air now," said Andy D. Birchfield Jr., a lawyer in Montgomery, Ala., who had expected to begin trying a Vioxx case in federal court in Birmingham as soon as next month.