the treatment that can unclog tired arteries filled with the atherosclerotic buildup that can lead to heart disease and stroke. But to most in the medical field, it is "unproven" at best and, at worst, a medical fraud.

Chelation therapy, the medical treatment that strips charged ions -- usually calcium and metals -- from the blood and then washes them from the body through the urine, generates little ambivalence within the medical community.

The therapy is accepted for certain conditions -- treating lead poisoning, for example, or removing other types of metals from the body, such as iron or radioactive materials. But questions arise when chelation is touted as doing for clogged arteries what Drano does for clogged pipes. There also are claims that chelation can reverse senility, heal ulcers, improve memory and relieve the symptoms of arthritis, Parkinson's disease and multiple sclerosis.

Chelation therapy "meets all the criteria of a health fraud," said Dr. Victor Herbert, chief of the hematology and nutrition research laboratory at the Bronx Veterans Administration Medical Center and coauthor of "Vitamins and Health Foods: The Great American Hustle."

The treatment, Herbert said, "is promoted with the claims that it is effective in widening narrowed coronary arteries. But the promoters who make millions of dollars from their promotions have never produced any evidence that it does widen coronary arteries."

But now, a drive is on to determine whether or not chelation therapy is safe and effective treatment for hardening of the arteries.

Members of the American Institute of Medical Preventics, proponents of chelation therapy, plan to seek approval next month from the Food and Drug Administration (FDA) to use a chelation drug in a clinical trial on patients, said Dr. Ross Gordon, president of the Institute. If the FDA grants the request, Gordon said, the group will commission an independent laboratory to conduct the trial, testing whether chelation therapy can successfully treat peripheral vascular disease, more commonly known as hardening of the arteries in the legs.

"The bottom line is that either we be proven correct or incorrect once and for all," said Gordon, a general practitioner from Albany, Calif. who is also past president of the American Academy of Medical Preventics, a Los Angeles based group whose 400 members include many backers of chelation treatment.

Representatives of the FDA and the American Medical Association have within the past year called for a scientific study of chelation.

The term chelation comes from the Greek "chele," meaning claw. Chelating agents are used to extract substances, like a kind of chemical claw or magnet. The most common chelating agent is ethylenediamine tetraacetate (EDTA), but other substances, including many antibiotics, also have chelating properties. EDTA is approved by the FDA for such varied purposes as preserving mayonnaise and treating lead poisoning. It also serves as both preservative and anti-coagulator in test tubes used to draw blood for analysis.

Physicians who use chelation therapy for atherosclerosis typically hook their patients up to intravenous an tube that contains a diluted solution of EDTA. The EDTA drips slowly into the body over several hours. It is excreted through the urine over a period of several more hours. Some proponents of this kind of therapy advocate taking oral chelation tablets, which usually contain high doses of vitamins. According to FDA spokesman Bruce Brown, these tablets are currently being removed from the market.

The cost of a series of treatments, usually 30 to 40 sessions, given over a period of eight to 10 weeks, runs between $3,000 to $5,000 and is not covered by health insurance or by Medicaid or Medicare.

No one knows exactly how many patients undergo chelation therapy each year. Dr. Elmer Cranton, president elect of the American Academy of Medical Preventics, estimates that there are 200 to 300 physicians performing the procedure today in the United States. "We think we probably treat between 150,000 and 200,000 patients a year," said the American Institute's Gordon.

Like any medical treatment, chelation therapy has risks. EDTA attaches to calcium and removes it from the body. Many proponents believe that this is why chelation might help reverse atheroslcerosis. Plaques that accumulate in the arteries contain calcium, among other substances, and chelation proponents say that by leeching calcium from the body, it is possible to open up clogged arteries.

Detractors note, however, that calcium is essential for many reactions within the body and removing too much can be harmful. "Calcium and other heavy metals are necessary for muscle activity," explained Stewart Ehrreich, deputy director of the cardiorenal division at the FDA. Remove too much calcium, he said and "there's potential damage to the heart, nervous system and other muscles."

Since calcium loss is also associated with osteoporosis, a debilitating bone disease, critics like Victor Herbert contend that chelation therapists "are selling you osteoporosis and calling it a cure for heart disease."

"Chelation therapy, when injudiciously used, destroys your kidneys," Herbert also charged. One report published in the Journal of the American Medical Association described a patient who had to go on kidney dialysis -- and stayed on it until he died -- after undergoing chelation treatment for a circulatory problem. Other reports have connected 14 deaths with chelation.

Those cases and others have led critics to call chelation therapy cardiology's version of Laetrile -- a drug once touted as a cure for cancer and later proven to have no effect on the disease. "The only difference," said one researcher at the National Heart Lung and Blood Institute, "is that patients don't have to go to Mexico to get it."

But chelation proponent Cranton said: "There has never been a death or malpractice case as a result of chelation therapy as long as it was administered according to the standards of the American Board of Chelation."

Yet numerous organizations, including the AMA, the FDA, the Health Care Financing Administration (which administers Medicare and Medicaid), the the American Heart Association, the American College of Physicians and the American College of Cardiology have warned consumers that there is no valid scientific proof to support the claims that chelation works for heart disease or any ailments other than metal poisoning.

Using chelation therapy for purposes other than metal poisoning is possible because of a regulatory loophole. EDTA is an approved FDA drug, and "any FDA approved drug may be used for any unapproved purpose by any licensed physician within their existing practice," said FDA's Brown.

The proposed $2.2 million study, Gordon said, will examine the effects of chelation therapy on two groups of 60 patients suffering from peripheral vascular disease of the legs. Also known as claudication, the condition slowly decreases blood circulation due to build-up of atherosclerotic plaque in blood vessels. The result is painful cramps, and in severe cases, the inability to walk more than a few steps.

Should the proposed study show that chelation therapy is safe and effective, Gordon said, he hopes it will "generate the political pressure to require the government to take a closer look" at chelation therapy as a treatment for arteriosclerosis throughout the body. "If we can improve the blood flow in the lower legs, he said, "chances are it could work in the vessels to the head, the heart, and the other organs in the body."