What would it be like if the U.S. had national health insurance? The past year has seen a plethora of proposals to overhaul the existing health care system and replace it with a more equitable one that guarantees coverage for more -- or all -- Americans.

Although the concept had little popular support a decade ago, these days groups ranging from the American Medical Association to the AFL-CIO to the Heritage Foundation, a conservative Washington think tank, agree that change is needed.

Despite a national health care bill that is expected to reach $666 billion this year, as many as 37 million Americans have no health insurance and 50 million more, the majority of whom are members of families headed by full-time workers, have only partial insurance coverage that would not pay for a serious illness. Every year, according to the Labor Department, 1 million people lose their health insurance.

The American public seems increasingly disturbed about the state of health care. When citizens of 10 developed countries were polled recently by Louis Harris and Associates, Americans were by far the least satisfied with their health care; 60 percent said they thought that the U.S. system needed a fundamental overhaul.

Below are the highlights of some of the major reform proposals now circulating on Capitol Hill and among federal policymakers. Several are expected to be introduced in Congress next year.

Physicians for a National Health Program -- The Canadian Model

This Massachusetts-based group of 3,000 physicians has proposed a national health program modeled on the 20-year-old Canadian health system.

Every American would be covered under the plan, regardless of income, age or health status.

This is the most sweeping of the proposals now circulating; it would phase out private insurance and replace it with a system that would be solely funded by the federal government. The program would be administered by the states.

Americans would be issued a national health plan card, similar to a credit card, which they would present at the hospital or doctor's office of their choice. Consumers would never receive -- or pay -- a bill.

Standard fees for each procedure and specialty would be set by state and regional boards, as is now the case with Medicaid and many insurance companies. Nursing homes and hospitals would receive an annual lump sum payment.

Doctors would be unable to charge more than the government permits. They would be paid according to the established fee schedule. Coverage would include standard medical care, mental health treatment and care for long-term, chronic illness.

Basic Health Benefits for All Americans Act

Sen. Edward M. Kennedy (D-Mass.) and Rep. Henry A. Waxman (D-Calif.) sponsored this proposal, which would require employers to provide basic health coverage to those who work more than 17 1/2 hours per week and their families. Those who don't meet this criterion would be eligible for a federal-state program that would provide subsidized health care.

Supporters argue that this approach would be least disruptive to the current health care system, because 72 percent of Americans now are receiving health coverage under employer-based insurance plans. The new plan would be administered by states under federal guidelines.

Employers would cover 80 percent of a benefits package that would guarantee major medical coverage such as physician and hospital services; it would also include prenatal care and catastrophic coverage. How much people would pay would depend on their income. Deductibles would be limited to $500 per family, except for prenatal care. The proposal also includes tax incentives that would make the benefits package affordable for small or start-up businesses.

For those in the public program, the benefits would be identical to the employer-based plan. The entire system would be phased in by the year 2000.

U.S. Bipartisan Commission on Comprehensive Health Care (Pepper Commission)

The Pepper Commission plan, issued three months ago, calls for universal health coverage through a combined job-based and public system.

Employers would provide health insurance for workers and their families or contribute to a public system that would also cover the unemployed. Under the plan, a minimum benefits package would include physician and hospital care, as well as preventive care, and workers would share some of the cost.

The Pepper plan also includes substantial insurance reform and, like the Kennedy-Waxman proposal, would provide financial help for small businesses that had trouble affording insurance and contains provisions for long-term care. The severely disabled of all ages would receive three months of nursing home care, and people would not have to divest themselves of their assets in order to qualify for government assistance.

Health Access America

The American Medical Association, which represents nearly 300,000 of the nation's doctors, last spring released a proposal that would increase access to health care by requiring employers to provide coverage for all full-time employees and their families.

The AMA has proposed a "minimum benefits package" for those who currently do not have coverage; the model program would cost employers approximately $1,700 annually per worker. The AMA plan would also expand Medicaid to include everyone below the poverty level. Currently, Medicaid covers only about 40 percent of the poor.

The AMA advocates the establishment of "risk pools" in all states to make health care available to the medically uninsurable as well as to those who could not afford an individual health policy. The plan also includes provisions for Medicare and malpractice reform.

Health Care Financing for All Americans

This proposal by the Washington-based Health Insurance Association of America (HIAA), the industry trade group, advocates major reform of the troubled small business insurance market.

Under the proposal, there would be a limit on insurance premium costs for small businesses. The average monthly premium for small businesses rose from $838 in 1978 to $1,836 in 1987, according to the National Federation of Independent Business.

The plan also includes protection for so-called "high risk" employees -- people with serious health conditions such as cancer. If a worker changed jobs or an employer changed insurers, new restrictions on pre-existing conditions could not be imposed. Like the AMA, the HIAA advocates the expansion of Medicaid to include all of those below the poverty line; it also supports the establishment of state risk pools for the medically uninsurable.

The HIAA advocates that insurers be allowed to sell cheaper "no frills" plans by exempting them from demands that they cover certain conditions, such as alcoholism or assistance for handicapped children. The insurance industry says that these mandates, which vary by state, have helped drive up the cost of health insurance.

Constance Matthiessen is a writer with the Center for Investigative Reporting in San Francisco.