One of the least-publicized features of the Medicare reform bill President Bush signed Monday may be the most revolutionary in the long term: Health Savings Accounts.

The tax-free HSA plan Congress created will allow qualified Americans under age 65 to accumulate savings throughout their working lives. The money is used to pay medical expenses not reimbursed by insurance.

Unlike the current "flexible spending" accounts, workers do not forfeit unused funds at the end of each year. The accounts represent personal wealth that can be passed on and inherited.

Best of all, the HSA program starts next month.

"Health Savings Accounts are huge. They have the potential to transform how we do health care in this country," said Rep. Rob Portman, R-Ohio.

Portman argues they will encourage personal responsibility and foster smart consumerism. As Americans shop around for health services they pay for with savings they own, they could encourage greater competition for health goods and services.

Other facts about HSAs:

• Contributions, build-up and distributions are all tax-free.

• The account owner, employer or a family member may make contributions.

• A worker must have a health plan deductible of at least $1,000 ($2,000 family) to qualify; however, there is no income test.

• Up to 100 percent of the deductible level may be saved each year, with a maximum of $2,600 for individuals - a figure that will be indexed to inflation.

• Workers ages 55 to 65 can save up to an extra "catch-up" $1,000 a year to build accounts.

• An account can be rolled over tax-free for a surviving spouse to use for health care. A non-spouse will pay income tax on the proceeds, and can't use it as a medical account.

Critics say MSAs will draw young, healthy workers out of the insurance pool, driving up costs for everyone else. But by encouraging savings and letting consumers make competitive choices in health-care purchases, they create a mind-set that should keep medical care more affordable in the long run.

HSAs won't be the answer for everyone, but they will benefit Americans who struggle with high-deductible plans and large out-of-pocket expenses. They will be a boon for future generations of seniors.