The health gap is widest for African Americans. In practically every type of illness and cause of preventable death but suicide, African Americans suffer and die younger, faster and at higher rates than whites. Fewer black women than white women get breast cancer, but more black women die from it. African American men have the highest rate of prostate cancer in the world.
The life expectancy for blacks is 6.5 years lower than for whites, with the biggest killer being high blood pressure, which leads to greater rates of stroke, heart attack and kidney failure.
Other minority groups fare better. In fact, the life expectancy for Asians and Hispanics is generally higher than for whites, and the life expectancy for American Indians is only slightly lower. Even so, members of these groups endure higher rates of certain diseases and graver consequences.
Compared with whites, Hispanics and American Indians have two to three times the rate of diabetes, and the numbers are growing fast. Vietnamese American women, meanwhile, contract cervical cancer five times more often than whites.
And AIDS, once a disease of middle-class gay white men, is becoming more common among minorities. In 1997, four times as many Hispanics and eight times as many blacks as whites contracted the deadly virus.
What's more, evidence suggests that immigrants lose many of the health advantages they bring to this country as they adopt the American way of high-fat, fast-food eating and sedentary living, and lose ties to their extended families and their culture.
All of this has caught President Clinton's attention. He has proposed spending $400 million over five years to ``close the gaps'' for minorities in six areas: infant mortality, cancer, cardiovascular disease, diabetes, HIV and immunization.
With U.S. demographics changing and minority groups projected to make up more than half the population by the middle of the next century, continuing to do little or nothing sets the stage for a major - and costly - health crisis. The consequences would be ``serious,'' said U.S. Surgeon General David Satcher, the point man on the President's race-and-health initiative.
``We're at the point now where these disparities actually define our health status in this country,'' Satcher said.
Government action has been piecemeal at best. Researchers, most of them white, have simply assumed that medical breakthroughs would ``trickle down'' to minorities. And the medical establishment - the American Medical Association has referred to the gaps as a ``nightmare'' and ``this collective shame of neglect'' - has done little to close the gaps.
Plus, those who are sickest often remain unaware that it is their own smoking, drinking and unhealthy eating habits that are making them so. Blacks have the worst nutrition of any ethnic group, despite years of well-meaning public-health education campaigns - campaigns that often miss the very minority communities that most need them.
Louis Sullivan, secretary of Health and Human Services in the Bush administration, described the official response this way: ``Nice words, no action, and protestations to the contrary when the issues are raised.''
``These gaps,'' said Jim Marks, a top official at the federal Centers for Disease Control and Prevention, ``have been our greatest failure. They just haven't been viewed as a priority. But we've got to recognize that they're changeable - and unacceptable.''
The poor's risk of dying younger is, and always has been, three times higher than that of the rich, says Bruce Link, a social epidemiologist. That risk has remained constant even though the killers of 100 years ago were infectious diseases, such as cholera and smallpox, and the killers of today are chronic illnesses, such as heart disease and cancer.
Poverty is a key reason why African Americans' health statistics are so bad. About 28 percent of the nation's black citizens are poor.
Last month, Health and Human Services released a sweeping report that found that there is a stair-step health pattern from rich to poor that holds true for virtually every risk factor, every disease - whether chronic, such as cancer, or communicable, such as HIV infection - and every cause of death.
The same economic ladder is found within racial and ethnic groups. For example, wealthier blacks not only live longer, healthier lives than poor blacks but also report that they are in better health than middle-income and poor whites.
Yet economics does not explain everything. Poverty accounts for only about one-third of the health differences, according to the CDC's Marks.
For instance, a black baby is more than twice as likely as a white baby to die before his or her first birthday. And the gap is just as wide or wider between higher-income, college-educated African Americans and whites as between lower-income African Americans and whites. Babies of largely poor West African immigrants, however, survive just as well as whites.
Nor does poverty explain what scientists call ``the Mexican Paradox.'' The poverty rate is high for Mexican Americans, and many have no health insurance, yet they are less likely than either whites or blacks to die from common illnesses, such as heart disease or cancer.
So, if not poverty, what accounts for the difference? It could simply be the sense of having - or not having - control over one's life. Racism can rob that sense of personal control.
In a new, and controversial, area of study, some researchers say that experiencing discrimination influences health by increasing stress and raising blood pressure. Researchers in Detroit surveyed mundane racism - being eyed with suspicion as a potential shoplifter in a store or being treated as less intelligent - and found it directly related to the ethnic health gaps.
``Even crude, self-reported discrimination seemed to be linked and crucial to health,'' said Dr. David Williams of the University of Michigan.
He said ``migration'' studies only strengthen the connection between health and social conditions. West Africans generally have low blood pressure, and blacks in the Caribbean have slightly higher blood pressure, but for African Americans, high blood pressure is epidemic.
Such facts would seem to disprove any biological basis for the health differences among ethnic groups. Still, scientists using federal money are looking to see whether there is a genetic explanation for why various groups are more prone to certain conditions.
Another common perception holds that if more members of minority groups, particularly blacks, were to have health insurance and go to doctors more often, they would be healthier. But some cancer studies of active-duty military personnel - who share equal insurance, equal access to doctors, and equal treatment - still show that blacks have higher incidences of cancer and higher death rates from the disease than whites.
Even with good health insurance, many minorities receive substandard care. Studies published in the Journal of the American Medical Association and the New England Journal of Medicine have shown that blacks, in particular, receive far less aggressive or outdated treatment - even when their conditions and health insurance are identical to those of whites.
Doctors are less likely, for example, to perform high-tech, diagnostic procedures on blacks or to go to extreme measures to keep them alive should they go into cardiac arrest on the operating table.
In addition, whites are two-thirds likelier than nonwhites to receive kidney transplants, and when hospitalized for pneumonia, whites are likelier than blacks to receive intensive care.
And whites with HIV are far likelier than blacks with HIV to receive advanced drug therapies - a trend that slowed the white death rate from AIDS by 28 percent from 1990 to 1995 but slowed the black death rate from AIDS by only 10 percent during that period.
Poverty, racism, genes, unequal medical treatment, dangerous and stressful and isolated environments, risky behavior, unhealthy lifestyles - no one really knows how much each of these factors contributes to the ethnic health gaps because, until recently, no one had looked.
Until 1992, more than 90 percent of all federally funded clinical trials, where the latest and most innovative drugs and technologies are tested, consisted of white men only. Though a 1993 law changed that, requiring that such research include women and minorities, only a scant number of studies are exploring ethnic health differences.
And while there is only a handful of minority scientists in the country - about 4 percent of all medical-school faculty members - even fewer sit on the panels at the National Institutes of Health that set the nation's research priorities.
Researchers say one problem is rooted in the minority communities themselves: Many members of minority groups, steeped in a culture of mistrust, are unwilling to participate in studies that could help understand and improve their health.
``These kinds of studies are just seen as too difficult,'' said Walter Kukull of the University of Washington, who has had trouble attracting Asian Americans into studies.
Indeed, a recent survey by Emory University's School of Public Health found that minorities believe in the benefit of medical research but do not believe it will benefit them.
Such suspicion, though, is not insurmountable, experts say, and the studies, while labor intensive, are not impossible to do.
``It's the same as if you were to go to Guatemala: You try to understand the population first,'' said Dr. DeJuran Richardson, who is involved in the first large study of blacks and stroke. ``The idea that this is impossible is so entrenched that this is like flying: Until someone does it, no one's going to believe it can be done.''
As a practical matter, the future rests on the nation's minority groups as they become a dominant part of the population and workforce.
``We're so worried about our Social Security and our retirement income, but we don't seem to realize that these are the people we will need to be employed to take care of us in retirement,'' said Victor Schoenbach of the Minority Health Project at the University of North Carolina at Chapel Hill.
``The less physically healthy and emotionally stable these minorities are, the more disadvantaged we all will be.''
* Tomorrow: How migrating to the United States can be harmful to your health.