It is a truism that black people do not trust the medical establishment and are reluctant to volunteer for experiments.

And why should they volunteer, the story goes, given the widely known history of Alabama's Tuskegee Institute, where for decades doctors withheld medical treatment from several hundred black men with advanced syphilis as part of a sordid federal study?

"There's just this wide assumption that gets repeated all the time," said David Wendler, a bioethicist who studies race issues at the National Institutes of Health. "We wanted to see what the data really show."

Those data, released yesterday, shoot down the myth.

Given the chance to participate, minorities volunteer at least as often as whites do, according to the first study to measure response rates directly. And although minorities are indeed underrepresented in research, the reason appears to be that doctors and scientists reach out to them less.

"You have to stop blaming the victim here," said NIH bioethicist Ezekiel Emanuel, who with Wendler led the new research, published in yesterday's online edition of the journal PLoS Medicine. "When you see it's about access -- not bringing enough minorities in -- that means the responsibility is on us, the researchers and research institutions."

Experts in minority medicine said they were gratified to see objective evidence supporting what they have long believed to be true.

"African Americans are quite willing to participate once barriers are removed," said William B. Lawson, chairman of psychiatry at Howard University. "Access, more than attitude, is the major factor."

Several studies have documented that minorities, and in particular blacks, distrust the medical establishment.

A survey released in February, for example, found that about half of blacks believe that a cure for AIDS exists but is being withheld from the poor. One in six said they believe the government created AIDS as a means of controlling black population growth.

Such attitudes have long been attributed, at least in part, to lingering resentment over the experiments at Tuskegee. For 40 years until 1972, the U.S. Public Health Service supported that study of nearly 400 black men, most of them illiterate. None were told that treatment for their disease was being withheld, even as they became blind and fatally brain-damaged.

President Bill Clinton, offering an apology to the eight surviving subjects in 1997, called the experiment "clearly racist."

Although studies have confirmed low minority participation rates in research, no one had done a study to see whether distrust explained that fact.

Having a negative attitude about research is one thing, Emanuel said, "but are you eligible? Are you even offered the study?"

Those questions are difficult to answer. Most studies do not reveal how subjects were enrolled or offer racial data for those who said "yes" against those who declined.

To find out, Wendler and Emanuel -- both with the NIH's department of clinical bioethics -- along with seven colleagues, conducted a comprehensive computer search of published health studies going back more than 20 years.

They found 20 studies that reported consent rates by race and ethnicity. Some were research surveys in which participants were simply asked to provide personal medical information. Other studies involved new medicines, and still others tested surgical procedures.

All told, the team documented the enrollment decisions of more than 70,000 individuals.

For the three simplest studies, consent rates were the same for blacks, Hispanics and non-Hispanic whites (about 8o percent). For the 10 studies involving medicines, rates were the same for blacks and non-Hispanic whites (about 45 percent) and higher for Hispanics (about 55 percent). And for the seven surgical studies, consent rates were the same for whites and minorities (about 55 percent).

NIH Deputy Director Raynard S. Kington, who helped run the new study, said the results rang true to him. When years ago, as chief of the nation's largest health survey, he sought recruits from communities black and white, he often found poor minorities more willing than wealthy whites to volunteer.

The new data shift the burden of responsibility from research subjects to the researchers, Kington said, and suggest that efforts to improve minority participation through educational campaigns need to be rethought.

"If the main driver is not an attitude problem on the part of minorities, then doing interventions to change those attitudes of minorities is not going to solve the problem," Kington said.

Troy Duster, a sociologist at New York University, said there are several possible explanations for why blacks remain willing to participate in research despite their documented misgivings. The higher toll they suffer from several chronic diseases may motivate them to contribute to medical knowledge, Duster said. Some may also see it as an opportunity to get high-quality care that they would normally be unable to afford, he added.

Vanessa Northington Gamble, director of the Tuskegee University National Center for Bioethics, said the work strengthens her sense that it is backward to say that blacks are "distrustful" of the medical system. She prefers to speak of medical institutions' "lack of trustworthiness," she said, to emphasize that it is the institutions' responsibility to gain people's trust.

"This study shows that once you get African Americans to the place and educate them and ask their consent, they consent at the same rates as non-African Americans," Gamble said. "We need to figure out what it takes to get these people into the system and to that interview."

One emerging strategy is to reach out beyond the specialists and other higher-echelon doctors who do much of the recruiting for U.S. clinical studies.

"For research involving interventions in subspecialties like cardiology and asthma, patients have to be in the specialty medical system to even know that those studies exist," Emanuel said. "If you're a minority in America, your chance of having a doctor in that system is smaller, which means you're not offered a chance to participate."

Recently, Emmanuel said, NIH has entered into collaborations with local health clinics to accomplish just that.

President Bill Clinton and Vice President Al Gore appear in 1997 with Herman Shaw, who was part of the Tuskegee Syphilis Study. The 40-year study, in which treatment for advanced syphilis was withheld from nearly 400 black men, has been used to reinforce the truism that blacks are reluctant to volunteer for medical experiments.