(FORTUNE Magazine) – Next time you visit an ATM, you may get a commercial along with your cash. Thousands of automated teller machines are becoming mini-media outlets, broadcasting TV ads and distributing print messages along with $20 bills.

Some ATMs show banners or 15-second video spots on their small screens while processing transactions. Others print messages or cents-off coupons on the receipts they spit out. Sponsors that have tested ATM ads include Compaq Computer, Sears, Nissan, Paramount Pictures, and Food.com.

The idea, of course, is to deliver the one-two punch of a TV and print ad to a captive consumer who's about to grab a fistful of cash. "People have to watch the screen to complete the transaction, so you have the undivided attention of your audience," says Mike Szimanski, president of ATM Advertising, a Baltimore startup that matches advertisers with ATM owners. Several banks, including Wells Fargo of San Francisco and PNC Bank of Pittsburgh, have formed ad sales operations to jump-start the category; some bankers figure that ad revenues could help reduce unpopular surcharges on ATM transactions. There are around 270,000 ATMs across the U.S., about half of which are owned by banks, according to the ATM Industry Association of Peewee Valley, Ky.

Given that advertisements already appear on New York City subway tickets and Massachusetts Turnpike toll receipts, ATM ads were probably inevitable. Using cash machines, sponsors can target messages to particular markets or upscale zip codes, or only to customers located in malls or drugstores. (In an early experiment, a handful of San Diego-area ATMs ran movie trailers for The Full Monty.) In theory, ads could be aimed at individuals, since an ATM owner knows who owns the card as soon as it's plugged in. ("Running low on cash, Mr. Jones? Consider a home equity loan from Main Street Savings.")

For now, though, the market is immature and hopelessly fragmented. Many ATMs are not equipped to deliver ads. Even Szimanski, whose firm has put together a network of about 20,000 ATMs, remains shut out of some markets. "It's been an uphill battle," he admits. "But only because this is so new." Banks and media buyers worry about customer resistance. Says Andrea MacDonald, owner of MacDonald Media, an ad agency that specializes in out-of-home media: "You have to walk a fine line between being innovative and being annoying." Maybe so, but seeing an ad beats paying $1.50 to get $60 from your account.

--Marc Gunther