"It's almost pure profit for us," a bank executive talking off the record admitted. "There are some incremental accounting fees, but other than that, (foreign-exchange) fees drop right to our bottom line."

You'd think making a pretty penny on business travelers when they are out of the country would be enough for the banks. Nope. In the last year or so, many have changed how they define a foreign-currency transaction. If your merchant—an international airline, for instance, or even a seller on eBay or Amazon Marketplace—uses a foreign bank to process your charge, you'll pay the currency exchange fee. You don't even know it's happening because the merchant is billing you in dollars and the charge appears on your card statement in dollars. But since the charge was routed through an overseas bank, your financial institution will take its 3 percent of flesh too.

(By the way, this flavor of foreign currency charge is partially fueled by an equally offensive practice called "dynamic currency conversion." That's when a retailer or restaurant owner overseas will helpfully suggest that he can handle the currency exchange on the spot and charge your card in U.S. dollars. Needless to say, the exchange rate you'll get is awful because the merchant receives a hefty piece of the currency transaction. Then your bank or financial institution will charge you its foreign currency fee atop the converted price anyway.)

Can you beat the system? Yes, but only if you pay careful attention to the game and choose your cards wisely.

There are a few cards—most notably, some elite charge products offered by Schwab in conjunction with their accounts—that do not impose foreign currency fees. Some international banks (including Citi and HSBC) offer a reduced rate or waive the currency fees for customers who join special bank programs that require high balances in checking, savings and other investment vehicles. A few specialty card issuers such as USAA limit fees on some cards to 1 percent.

Then there is Capital One, a fast-growing bank and credit card issuer that has emerged as a formidable niche player with business travelers. Capital One credit cards currently do not impose a currency exchange or cross border fee. Banking cards tied to its checking, savings and money-market accounts are free from overseas fees, too.

Capital One's competitors deride its no-foreign-fees policy because they claim the bank's customers tend to be lower-income types who aren't likely to travel overseas. My reaction? So what. Demographics notwithstanding, it is clear that plenty of higher-income business travelers like me carry Capital One credit and ATM cards specifically to use overseas.

And for all their bluster, Capital One's competitors have realized that one way to win the business of business travelers is to create products that are free from foreign exchange folderol.

Consider the new credit card that Chase has unveiled in conjunction with Priority Club Rewards, the frequent guest program of the Holiday Inn and InterContinental family of hotels. Besides the usual affinity card perks (elite status, bonus points for hotel charges, free stays), the Chase Priority Club Select Visa does not charge foreign exchange fees.

Chase, the nation's largest card issuer, will also soon unveil its first credit card for the Hyatt Gold Passport frequent guest program. The much-anticipated card was announced earlier this year, but neither Chase nor Hyatt will discuss its features before the product is officially introduced in the next few months. But one hot (and plausible) rumor is that the Hyatt-tied card will also be free from foreign exchange fees.

"I wouldn't say [foreign exchange fees] are a new battleground in the travel business," one credit card executive told me last week. "But I will say that Capital One has gotten people's attention. "The theory that business travelers are price insensitive is silly. They know when they are getting dinged 2 or 3 percent for no reason."

The Fine Print…

One more complication to using your credit, debit or ATM cards overseas: Much of the world is moving to cards that use an embedded chip rather than the magnetic stripe preferred by U.S. financial institutions. Some overseas point-of-sale devices (ticket machines, for example, or "swipe" terminals at retailers) no longer accept cards that don't have the new chip technology. So make sure you have local currency.