CHICAGO -- Worried about growing resistance to genetically modified foods, some of the world's biggest biotechnology companies are mounting a huge lobbying and marketing campaign to counter their critics and combat what they call a rising wave of anti-biotech hysteria.

Makers of genetically modified seeds have taken a beating this year in Europe, where critics have sabotaged test plots of altered crops and have fostered widespread distrust of what they call Frankenstein foods.

Now that concern is beginning to grow in the United States. Environmental groups are stoking opposition through lobbying and full-page advertisements; federal lawmakers on Wednesday introduced legislation that would require labeling of food made with genetically modified crops, and regulators are re-evaluating everything from food safety to the effects bioengineered crops may have on the monarch butterfly.

At stake in this contest for American public opinion are billions of dollars in investments by the biotechnology industry and American farmers who have rapidly adopted products like corn, potatoes and soybeans that have been engineered to resist pests or producer higher yields.

Until recently, the leading biotechnology companies were reluctant to respond to criticism in this country for fear of making the novel foods an issue. But some biotech executives now say that there is a sense that the tide may be turning against genetically modified foods and that urgent action is needed.

And so in recent months, the Monsanto Company, Du Pont, Novartiscoei A.G. and other biotech companies have formed a series of industry-wide alliances and have set aside tens of millions of dollars to fight what they view as an ugly campaign that has vilified the companies -- calling Monsanto, for example, "Monsatan" and "Mutanto," -- and has misrepresented their products.

"The protest industry has gone too far," Edward Shonsey, chief executive at Novartis Seeds Inc., said in an interview. "They've crossed the boundaries of reasonableness, and now it's up to us to protect and defend biotechnology. As a result there's a combined effort to get the facts out there."

Members of the alliances are financing scientific research, organizing educational forums, lobbying legislators, regulators and farm organizations, and using their own Web sites to promote the benefits of genetically modified, or G.M., products. The members have also retained three major public relations concerns in recent weeks. And many are pooling their resources and preparing a global advertising and public relations campaign.

"All these forces are coming to bear where we're going to have a really big battle," said Todd Duvick, a food industry analyst at Bank of America. "We already have huge quantities of G.M. foods and there are companies that want labeling and companies that don't want them; it's creating a logistical nightmare. Meanwhile, all the biotechnology companies are trying to protect themselves."

The debate centers on a technology that can borrow a genetic code from plants or animals and transfer it to a plant to give it a desired trait. This year, 20 to 45 percent of American corn and soybeans were grown from seed engineered to produce its own insecticidal toxin, and those crops have found their way into many processed foods. Backers say biotechnology may eventually lead to crops that have extra nutrition or can thrive in adverse weather.

But some consumer advocates and scientists, particularly in Europe, say that not enough research has been done to prove that food made from genetically altered crops is safe to eat. In response, federal regulators say that no studies have proven that food made from genetically modified products is harmful to eat, and that all biotech products now on the market have been deemed safe.

Another concern is the possible effect such crops might have on the environment. An increasing number of studies suggest that genetically modified plants could interact with the environment in hazardous ways, like creating a hard to eradicate super weed, and that regulators are not demanding the proper studies to assess the risks.

With critics gaining ground in the United States, the biotechnology companies feel they need to act. But their campaign is not unified. Monsanto, whose aggressive efforts to gain acceptance for its genetically modified products backfired in Europe, recently retained Burson-Marsteller, a global public relations firm, at an annual cost of millions of dollars, according to people who reviewed the deal.

Monsanto, whose stock price has suffered over the past year because of growing concern about the viability and profitability of its biotechnology division, is now trying a two-pronged effort to educate consumers and reach out to its critics.

"We look at this as a much more positive, pro-active dialogue with the public, which has the right to know more about the benefits of biotechnology," said Nick Rosa, a senior vice president at Monsanto in St. Louis. "We are not interested in a guerrilla response. There are many coalitions interested in communicating on biotech and in many instances we are working with them. We believe that the benefits of biotechnology need to be told."

Monsanto is even meeting with some of its most vocal opponents. A month ago, the company's chief executive, Robert B. Shapiro, addressed a gathering of the environmental group Greenpeace. And top executives at Monsanto, including Shapiro, are planning to meet soon with Jeremy Rifkin, an influential commentator on science and technology to whom biotechnology is a "Faustian bargain." The meeting was arranged by Ralph Nader, the consumer advocate. Du Pont is taking a conciliatory approach.

"Public concern has been aggravated by the perception that we in industry have often acted as though public fears are not legitimate and are the result of ignorance," Charles O. Holliday Jr, the chief executive at Du Pont, said in a speech last September. "Unfortunately, many in the industry have been reluctant to address concerns about the risks of biotechnology. But we have to listen to the people who are now raising alarms. We don't have all the answers and to pretend we do, or to brush off concern as unfounded, is to be arrogant and reckless."

Du Pont recently released a series of television commercials about the future, featuring the company's "to do list," which included research to "find food that helps prevent breast cancer."

Novartis Seeds U.S.A., however, is publicly acknowledging a spirited campaign to balance the flow of public information about biotechnology.

"I'm in four or five different working groups on this issue," said Shonsey, the chief executive at Novartis Seeds. "We're holding in-depth sessions with members of Congress, with universities and trade associations, the grocery manufacturers and food associations. Strategy is taking place to do that, you may even see TV and radio ads, even scientific conferences. We want a consistent message out there. We want a more balanced discussion."

Food industry trade groups are also rallying and recently formed the Alliance for Better Foods, whose Web site betterfoods.org, is devoted to promoting the benefits of biotech foods.

The organization, which is supported by groups like the Grocery Manufacturers of America, says it wants consumers to know not only that bioengineered crops resists pests and increases crop yields, but that the technology holds out the promise of creating more nutritious foods and perhaps even foods that could serve to prevent or treat medical ailments.

"You've seen the shrill statements and outrageous tactics by people who are attacking biotech foods," said Gene Grabowski, a spokesman for the Grocery Manufacturers of America and the Alliance for Better Foods. "Our site is intended to be based on fact; it's decidely pro-biotech but it's not intended to be strident."

The companies have reviewed their stunning public relations loss in Europe and now acknowledge that there were a number of missteps. "I think there was a certain naïveté in our initial approaches to the European market," Shapiro said in an interview. "We had been operating on a model that had been used in the U.S. If the question is have we learned anything in recent months in the sociology, the media orientation, yes we have learned something."

In many cases, the trade groups and other coalitions are expected to take the visible lead in the months to come. "There's a feeling that some of the companies have been vilified, and so it's more credible if scientists and academics and farmers stand up on the issue," said Carl Feldbaum, president of the Biotechnology Industry Organization in Washington, which is lobbying on behalf of Monsanto and others. "If it's the company people say, 'Well, it's got a commercial interest.' So it's better this way."

Some of the leading environmental groups, however, say they believe the new campaign will backfire because it will raise even more questions about biotech foods.

"They are under the misguided assumption that the more information they put out the more light at the end of the tunnel," said Rifkin, who is president of the Foundation on Economic Trends, an environmental group. "But the more information they put out the more questions people have about G.M. foods." He asserted that the products were dangerous and said, "They think it's public relations disaster but it's more than that."

Environmental groups in the United States pounced on the issue last May, when a Cornell University study showed that pollen from corn producing the insecticidal toxin Bt could stunt the development of monarch caterpillars in the laboratory. Since then there has been growing coverage by the news media of the concerns about the safety of genetically modified crops.

On Wednesday in Washington, a bipartisan group of 20 members of Congress introduced legislation that would require labeling of genetically engineered food products because of concerns about food safety.

In the coming weeks, the F.D.A. is planning to hold a series of forums on biotechnology, largely to solicit public opinion, and Agriculture Secretary Dan Glickman is expected to name a panel of experts to advise him on biotechnology issues; the Environmental Protection Agency is also expected to announce in the coming weeks how biotech corn can be planted, a decision that may be influenced by the recent restudies on the monarch butterfly.

In the scramble to influence this debate, a group of public relations officials apparently jumped the gun last week at a scientific conference here.

The conference, which was financed by the large biotechnology companies, invited representatives of the news media. Yet before the deliberations began, conference staff members issued a news release announcing that the meeting was expected to show that genetically engineered corn did not harm monarch butterflies, even though no scientists later polled by a reporter said they could draw such a conclusion and most of them acknowledged that their research was far from complete.

The conference and about half the studies presented were financed by the biotechnology industry. But the public relations officials insisted the meeting was strictly scientific.

"You can quibble with it but I think it was a low-key press release," said Libby Mikesell, a spokeswoman for the Agricultural Biotechnology Stewardship Working Group, a trade group financed by big biotechnology companies. "This just said: 'This is what we expect them to say, please tune in. There wasn't any interest in trying to spin it.' "

Several scientists, however, say they were told the conference could help influence the decision by the E.P. A. on biotech corn. "It's my understanding that they wanted to give some partial data to the E.P.A. by this date," said John Foster, a professor of entomology at the University of Nebraska.

The scientists say part of the reason they chose to release preliminary data, some of the studies with as little as 10 percent of the work complete, was pressure from farmers seeking more information.

Indeed, much of the debate about biotechnology is coalescing around seed sales to farmers. The nation's leading seed and biotechnology companies are trying to convince farmers of the viability of their products.

"They're doing a lot more hand holding," John Hawkins, a spokesman for the Illinois Farm Bureau. "Farmers are upset with low prices and now you have this technology with potential to lower their costs but foreign countries are saying 'we're not going to buy it or we'll have to label it.' "

And if farmers turn against them, the big biotechnology companies could face huge losses.

"Clearly everyone in the biotech industry is concerned," said Frank Mitsch, an industry analyst at Deutsche Banc Alex. Brown, a brokerage firm. "To some extent the year 2000 is going to be a lost year for them, and we're trying to see the order of magnitude."

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