The cards, which target the 4 million Social Security and Supplemental Security Income recipients without bank accounts, debuted this spring in four states—Texas, Arkansas, Louisiana, and Oklahoma—and are expected to be available nationwide by the end of the summer.

Those who choose to sign up for the debit program will receive a MasterCard debit card, which will be reloaded each month with benefit payments and secured with a personal identification number (PIN). The card can be used at ATMs to withdraw cash and at retailers for purchases and to get cash back.

Some usage fees are attached: Paper account statements will cost 75 cents; online bill-paying service will be 50 cents per bill. The first ATM withdrawal each month will be free; additional withdrawals will cost 90 cents each, and some ATMs may assess their own usage fees. International ATM withdrawals will cost $3 plus a 3 percent currency conversion fee.

DEBIT AT A GLANCE • Available this spring in Texas, Arkansas, Louisiana, and Oklahoma; rest of the country this summer. • Benefit payment will automatically reload on card monthly. • Watch out for fees, ranging from 50 cents to $3 or more per transaction, depending on how card is used.

Judy Tillman, commissioner of the Financial Management Service at the Treasury Department, says the debit card is a faster and safer way to deliver funds than mailing paper checks. In a small pilot study conducted last year in Illinois, 85 percent of debit card users said they were satisfied.

But consumer advocates warn that individuals must be vigilant in tracking debit card spending and fees. While debit cards carry some protection if lost or stolen, a consumer’s maximum liability depends on how quickly a loss is reported.

Debit cards “have a high risk of loss if stolen or abused,” says Ed Mierzwinski, consumer program director at U.S. PIRG, a public interest research group in Washington. “But it’s an improvement on getting a check and going to a check cashier and running out of money before the end of the month [because of deduction of cashier’s fee], or getting mugged on the way out of a check cashier.”