GOING the Distance" reads the advertisement, which shows four mountain climbers bursting with health, and promotes an anti- AIDS drug manufactured by Merck.

What's wrong with that?

Plenty, according to the Food and Drug Administration, which recently ordered that the Merck ad, as well as those of other companies featuring robust young men heaving javelins, riding bikes and crewing on sailboats, be pulled. Such portrayals, said the F.D.A., were "not generally representative of H.I.V. patients and do not adequately convey that these drugs neither cure H.I.V. infection nor reduce its transmission."

For their part, Merck officials originally defended their ads, saying they were part of a larger effort to get patients to talk to their doctors about treatment and to show that people were living longer lives on the drugs, but the company has since complied with the order.

Truth in advertising has long been considered an oxymoron. From political campaign spots to the perfect grill marks on hamburgers in Burger King television ads, advertisers have always improved upon reality. But the practice is much more contentious when it comes to medical advertising. After all, the risks associated with embellishing the appearance of fast food are appreciably lower than those having to do with creating misconceptions about a mortal disease.

"The standard for a false or misleading advertisement is whether the ad makes a material statement that is likely to mislead the consumer," said Kent R. Middleton, an advertising professor at the University of Georgia. "That's why when you get into the health field more statements are considered material, with greater consequences for consumers than candy advertisements or Coke ads."

In addition, Ronald Valdiserri, deputy director for the AIDS center at the Centers for Disease Control and Prevention, said that AIDS is different from most diseases in that almost everyone involved in fighting it — prevention advocates, drug companies, politicians and even the United Nations — has from the first crafted images of the illness to suit a specific set of needs.

In 1987, for example, the federal government decided to blitz the American people with a frightening message: anyone could get AIDS.

"If I can get AIDS, anyone can," said the son of a Baptist minister in one of the government's public service announcements.

The award-winning campaign, called America Responds to AIDS, helped catapult the disease into the public consciousness and convince public and private funders to underwrite the fight against it. But while the message of the campaign was technically correct, it was also somewhat misleading.

Yes, everyone faces some measure of risk. But 14 years ago, AIDS in the United States was overwhelmingly a disease of gay men and intravenous drug users, and their children. Yet references to drug use and sexual orientation in the America Responds to AIDS ads were removed under pressure from conservatives in Congress. The minister's son, for example, was gay, but that information was kept out of the script.

To be sure, prevention experts say that targeting the widest possible audience is not necessarily a bad thing when it comes to a disease like AIDS, particularly when one of the goals is to build not only awareness, but broad support for research and prevention measures.

But the decision to make descriptions of the new illness as unobjectionable as possible entailed real costs. For years, prevention advocates contend, the ad campaign — because of what had been left out — made it impossible for them to get federal health officials to set aside money specifically to educate drug users and gays. Much of the government's $600 million AIDS- prevention budget was used instead to combat the disease among college students, heterosexual women and others who faced a relatively low risk of contracting the disease.

THE United Nations may soon pay a similar price, said Patricia Siplon, an AIDS prevention advocate and political science professor at St. Michael's College in Colchester, Vt. By 2003, the world body hopes to begin spending $7 billion to $10 billion a year battling AIDS and other diseases with a campaign that will reach almost every nation on earth. But the United Nations has bowed to pressure from conservative states like Egypt, Sudan and Malaysia, as well as from the Vatican, which insist that no mention be made of prostitutes or gays, even in nations like South Africa, Thailand and Poland, where those groups constitute a large portion of the infected.

"What is so tragic this time is that the proportion of the problem is 20 times bigger, and there are many more people who are going to suffer because we are slow learners," Professor Siplon said.

Similar disinformation has been spread by the advertising used to promote anti-AIDS drugs, said Natasha Jenkins, an infectious disease market analyst in London for Datamonitor Healthcare, which does research for drug company advertising campaigns.

Since 1997, when the F.D.A. first allowed drug companies to market directly to consumers, "They have made it seem like there is a cure and a lot of people have stopped taking the same precautions because they feel that AIDS is being controlled by drugs," said Ms. Jenkins.

Her view is borne out in recent surveys, including one this year by the San Francisco Public Health Department that showed that gay men who said they rarely or never saw the AIDS drug ads were more likely to say they practiced safe sex.

"There is obviously a tradeoff in wanting and letting people know that there are treatments for H.I.V. infection," Dr. Validiserri, of the C.D.C., added. "But we also don't want to go so far that we minimize what is still a lifelong, incurable disease."

Christine G. Sinnock, a social worker at St. Jude Children's Research Hospital in Memphis, who works with children and young adults with AIDS, points to polls showing that although 75 percent of Americans thought AIDS was the country's most pressing health problem in 1987, that number had dropped to 45 percent in 1995 and to 26 percent by last year.

"The numbers make it seem as if we had found a cure, but it is really just that the drug companies are winning the image game," Ms. Sinnock said. "Whether it is the America Responds to AIDS campaign or the more recent ads by the drug companies, we have a history of creating misconceptions that have made this disease more difficult to fight on the ground level."