American medical care may be the most expensive in the world, but that does not mean it is worth every penny. A study to be released Thursday highlights the stark contrast between what the United States spends on its health system and the quality of care it delivers, especially when compared with many other industrialized nations.

The report, the second national scorecard from this influential health policy research group, shows that the United States spends more than twice as much on each person for health care as most other industrialized countries. But it has fallen to last place among those countries in preventing deaths through use of timely and effective medical care, according to the report by the Commonwealth Fund, a nonprofit research group in New York.

Access to care in the United States has worsened since the fund’s first report card in 2006 as more people — some 75 million — are believed to lack adequate health insurance or are uninsured altogether. And within the nation, the report found, the cost and quality of care vary drastically.

The findings are likely to provide supporting evidence for the political notion that the nation’s health care system needs to be fixed. Both presumptive presidential nominees, Senator John McCain and Senator Barack Obama, argue that the country needs to get more value for its health care money, even if they do not agree on what changes would be most effective. But few people these days defend the status quo.

“It’s harder to keep deluding yourself or be complacent that we don’t have areas that need improvement,” said Karen Davis, president of the Commonwealth Fund.

The study, which assesses the United States on 37 health care measures, finds little improvement since the last report, as the cost of health care continues to rise steadily and more people — even those with insurance — struggle to pay their medical bills.

“The central finding is that access has deteriorated,” Ms. Davis said.

Even some experts who are quick to point to some of the country’s medical successes, as in reducing the deaths from heart disease or childhood cancers, for example, also acknowledge the need for change.

“We need to generate better value in this country,” said Dr. Denis A. Cortese, the chief executive of the Mayo Clinic.

In some cases, the nation’s progress was overshadowed by improvements in other industrialized countries, which typically have more centralized health systems, which makes it easier to put changes in place.

The United States, for example, has reduced the number of preventable deaths for people under the age of 75 to 110 deaths for every 100,000 people, compared with 115 deaths five years earlier, but other countries have made greater strides. As a result, the United States now ranks last in preventable mortality, just below Ireland and Portugal, according to the Commonwealth Fund’s analysis of World Health Organization data. The leader by that measure is France, followed by Japan and Australia.

Other countries worked hard to improve, according to the Commonwealth Fund researchers. Britain, for example, focused on steps like improving the performance of individual hospitals that had been the least successful in treating heart disease. The success is related to “really making a government priority to get top-quality care,” Ms. Davis said.

The presidential candidates both emphasize the need to shift the country’s health priorities, to provide more medical care that helps prevent people from developing disease and that helps control conditions before they become expensive and hard to treat. And the mounting evidence indicates that such issues are not simply political talking points, said Len Nichols, a health economist at New America Foundation, a nonprofit group in Washington that advocates universal health care coverage.

More hospital executives and doctors understand their performance could be better, Mr. Nichols said.

Dr. James J. Mongan, the chief executive of Partners HealthCare System, a big medical network in Boston, agrees that “there’s substantial room for improvement.” Dr. Mongan is one of several health care leaders who is working with the Commonwealth Fund to develop a model for a better system.

Business leaders also see a pressing need for health care changes, said Helen Darling, the president of the National Business Group on Health, which represents big employers that provide medical benefits to their workers. The report “documents that it’s been as bad as we have been thinking it is,” she said.

But Ms. Darling and others were also heartened because some areas in the report said that the United States had shown marked improvement, including the measurements hospitals use to track how well they treated conditions like heart failure and pneumonia.

“It proves once again if you have quantitative information and metrics and make people pay attention, they change,” Ms. Darling said.

But the report also emphasizes the inefficiencies of the American health care system. The administrative costs of the medical insurance system consume much more of the current health care dollar, about 7.5 percent, than in other countries.

Bringing those administrative costs down to the level of 5 percent or so as in Germany and Switzerland, where private insurers play a significant role, would save an estimated $50 billion a year in the United States, Ms. Davis said.

“It kind of dwarfs everything else you can do,” she said.

Much of the high costs are attributed to the lack of computerized systems that may link pharmacies and doctors’ offices for filling prescriptions, for example, or that may enable insurers to more efficiently pay doctors’ bills.

“An awful lot of the waste in this system is the antiquity of the information technology,” Ms. Darling said.