Suddenly, celebrities who want to raise awareness about health problems are becoming as inescapable as, well, health problems. They're on talk shows, in news stories, on Web sites, at fund-raisers, even testifying before Congress.

Rob Lowe talks passionately about chemotherapy side effects. Michael J. Fox, about Parkinson's disease. Lauren Bacall, macular degeneration. Lynda Carter, irritable bowel syndrome. Dan Quayle, deep vein thrombosis. Camilla Parker Bowles, Jill Eikenberry, Michael Tucker, Meredith Viera, osteoporosis. Wynnona Judd, asthma. Noah Wyle, post-traumatic stress disorder, melanoma, and uninsured Americans - although not all together.

While some of these stars have embraced a health cause because they have the disease or for strictly altruistic reasons, most have an additional motive: They're getting paid by a pharmaceutical or health-care company that, not coincidentally, makes money diagnosing or treating the health problem.

This fact tends to get lost in the fine print of press releases, if it gets mentioned at all. Often, the celebrity is presented as the "spokesperson" for an awareness-raising campaign led by a nonprofit such as the National Osteoporosis Foundation or the American Lung Association. The celebrity may not even mention the company's product by name - just a campaign Web site or toll-free number sponsored by the company.

Relatively new but increasingly common, celebrity-driven health-awareness campaigns are defended by medical companies, nonprofits, celebrity brokers, and, of course, celebrities. They say it can empower consumers, improve health care, and save lives.

But critics are appalled. Stealth health-product marketing, they say, is blurring the distinction between advertising and education, giving celebrities undue medical influence, and contributing to soaring health-care costs.

"Often, there is a legitimate reason to try to raise awareness about a disease," said Ray Moynihan, a British Medical Journal editor who has researched drug-marketing practices. "The question is: Who is raising awareness, and why?"

Until recently, few thought to ask that question. Traditionally, big-name disease champions were easy to peg as humanitarians, shills, or confessors.

But last summer, after Moynihan and a few others began writing about the new breed of celebrity pitch people, CNN announced a new policy: Do ask, do tell. CNN had just broadcast an interview with actress Kathleen Turner, who talked candidly about her struggle with rheumatoid arthritis - without mentioning the arthritis drug makers who hired her.

The growing number of agencies that connect celebrities with health causes say they advocate full disclosure. One agency, Spotlight Health in Los Angeles, even posts an ethics statement to that effect on its Web site.

Yet the brokers acknowledge that, by contract, they cannot disclose how much their clients are paid. Nor do brokers have control over the sprawling network of publicists and promoters who may not be as forthcoming as the brokers would like.

Case in point: A New York City public relations agent recently sent a pitch letter offering interviews with Viera, cohost of a TV talk show, who is "spearheading" a National Osteoporosis Foundation campaign to encourage bone density testing. It gave no hint that Merck & Co., maker of an osteoporosis drug, is paying for Viera and the campaign.

(Asked through the public relations agent for an interview for this story, Viera, a former journalist, said she was too busy.)

Barry Greenberg, founder of 22-year-old Celebrity Connection in Los Angeles, is one of the few people making money from awareness campaigns who seems to have no illusions: "The world... wants to believe all this stuff happens spontaneously, without any combustion on the part of pharmaceutical companies... . What you need to understand about this [celebrity] community is that not everybody is rich, and a lot of this is motivated by income."

Greenberg told Variety magazine that compensation typically can range from $30,000 to $300,000, and sometimes go all the way up to $1 million and stock options.

Amy Doner Schachtel, president of Premier Entertainment Consulting in Essex Fells, N.J., thinks celebrities are "compensated appropriately."

"Someone could take this in a cynical way," she said, "but our goal is to get these celebrities out there to say 'See your doctor'... and 'Go to this Web site for more information.'... I forget which celebrity it was, but a celebrity said to me: 'If I can help one person, good for me.' "

Merck spokesman Tony Plohoros said the company "always tries to make [financial ties] clear." "The pure purpose," he said, "is to raise awareness."

Robert Bonow, president of the American Heart Association - which has a campaign with actress Rita Moreno underwritten by Takeda Pharmaceuticals and Eli Lilly - said it is "a purely educational program to raise awareness and understanding of the connection between cardiovascular disease, diabetes and insulin resistance. We are grateful to our corporate sponsors."

In Europe, where drug advertising aimed at consumers is illegal, educational information about diseases and treatments is published by independent drug bulletin groups that do not depend on industry support.

In the United States, direct-to-consumer drug advertising surged in 1997 when the Food and Drug Administration allowed TV ads, paving the way for a parade of drug endorsers including Bob Dole (Viagra), Dorothy Hamill (Vioxx), Joan Lunden (Claritin), and Lauren Hutton (Prempro).

Still, the FDA can stop a drug ad campaign if it contains false or misleading information.

Not so with a disease-awareness campaign.

"If you're talking about diseases and conditions, we don't regulate it," said Melissa Moncavage, director of the FDA's direct-to-consumer advertising review group.

Awareness campaign sponsors and creators say disease information is vetted by medical experts and often updated.

Even so, European authorities consider such material suspect. Last year, they rejected a drug industry proposal to provide consumers with information about treatments just for HIV/AIDS, asthma and diabetes.

The consumer advocacy group Health Action International cheered: "While [drug] industry representatives... have argued that the proposal was about providing information, public health groups... have emphasized that the proposal would actually allow promotion disguised as information to reach consumers."

Such promotion can change the doctor-patient relationship, said Barbara Mintzes, an epidemiologist at the University of British Columbia. In a study of family doctors in Sacramento, Calif., and Vancouver, British Columbia, she found they usually obliged when patients asked for a specific drug. In Sacramento, 7 percent of patients requested specific drugs, compared with 3 percent in Vancouver. (Canada has a ban on consumer-aimed drug ads, but it can't keep U.S. ads out.)

Studies show a strong correlation between prescription drug spending - growing at four or five times the rate of inflation - and increased sales of heavily advertised drugs.

Awareness campaigners see such trends as evidence that patients are being empowered to take charge of their health care.

Merck spokesman Plohoros said more than 5,700 people in Cleveland, Dallas and Atlanta took advantage of free bone density tests offered through the new osteoporosis campaign.

Whatever the merits of such campaigns, Moynihan believes the trend raises a more basic question: "Is it appropriate that companies shape the way we think about illness?"