Johnny Bitter calls it "ugly money." And he really can't explain why he is so attracted to it.

Bitter is the owner of Johnny Burrito, a lunchtime landmark in downtown Charlotte, N.C., jammed with customers from 11 a.m. to 3 p.m., most of whom pay in cash.

About five years ago, as Bitter counted and stacked the money at day's end, he found himself inexplicably drawn to marked bills, some stamped, some written or drawn on, some torn and crudely repaired with tape or -- Bitter's favorite -- staples.

"I don't know why I would pull them out," he said. "I'd say, 'Wow, look at the devil's horns on this one.' I've never drawn on money, never even thought of it. My wife said, 'What are you doing with all this money?' "

Now, Bitter collects bills that come across the lunch counter. He buys choice bills from the tellers in a nearby bank. And since last year, with the help of a friend, he even maintains a Web site, www.uglymoney.com, that displays more than 200 creatively marked bills.

Bitter has merely made a hobby out of something we've all experienced: discovering dollar bills with messages and drawings on them. Maybe it's a greenback with ball-point lettering around the margins that reads: ST. LAZARUS, ANYONE WHO RECEIVES THIS BILL WILL BE BLESSED WITH A LOT OF MONEY IF THEY WRITE THIS MESSAGE ON TEN OTHER BILLS. Maybe it's a fistful of slogans: LEGALIZE POT. DEPORT ALL ILLEGAL ALIENS. GAY MONEY. Maybe it's a dollar bill marked with a mystery: SEE WHERE I'VE BEEN. TRACK WHERE I GO NEXT! WWW.WHERESGEORGE.COM.

No matter what the content of your doctored dollars, it's easy to get hooked on marked money. You can get swept up in the small mysteries, the snippets of personal expression piggy-backed on currency, flowing from cash register to wallet to tip jar to deposit box to bank teller, and on and on, like messages in bottles from unknown cast-aways.

Bill-marking is the child of the graffiti tagging movement of the 1980s. It's the grandchild of the "Kilroy Was Here" markings, which were ubiquitous during World War II. It's the great grandchild of the hobo markings on freight trains during the Great Depression.

You can trace the phenomenon all the way back to cave painting if you want. Yet there are aspects of the money marking phenomenon that tie as neatly into our technologically sophisticated times as eBay or Internet chat rooms. In the end, money marking is a small way to test our liberty on a symbol of that liberty at a time when information technology may be threatening our liberty.

Bitter says he believes the purpose of marked money is the basic human drive to communicate.

"The bills make people think for just a minute," he said. "Money is so basic to our everyday life. A lot of people want to make a statement, get it out to a lot of other people and remain anonymous. It's amazing to me, what you find. The devil is a popular drawn theme, so is any sort of facial hair. I've seen drawings of Homer Simpson and Gene Simmons over Washington's face and a lot of political statements. The Santa Claus dollar is a good one. I've seen George Washington with Indian feathers and small pock marks -- that's a strong political statement. So is the Confederate flag stamped over Lincoln's face."

One of Bitter's favorites is an enraged rant that reads in part: MINIVANS ARE THE PURGATORY OF THE FAMILY ROAD TRIP. THE FAMILY REUNION IS THE EVERLASTING FLAME THAT BURNS YOUR FLESH AND EATS YOUR SOUL.

Most money messages are considerably more mundane. HAPPY BIRTHDAY is perhaps the most common. There are also phone numbers, addresses and columns of arithmetic. And then there was the recently found dollar bill marked with Subway sandwich-making instructions: COLD CUT COMBO, PARMESAN BREAD, LETTUCE, TOMATO, CHEESE, PICKLE, HONEY MUSTARD, SALT AND PEPPER.

But once in a while you find something really intriguing, like a 1995 dollar bill anachronistically stamped: WELCOME HOME VIETNAM VETS . Or a rap-inspired love letter written in red, which reads in part: CONTINUE TO KEEP IT GANGSTA FOR ALL THESE HOES! Or a cryptic plea: DON'T LEAVE ME HAUNTED.

The inscrutability of the bills is a large part of their charm. But it's impossible to come across them without wondering: What do they mean? Who's making them? Where? Why?

In the case of Hank Eskin, marking money grew out of simple curiosity.

"I was going to lunch one day when I saw a dollar bill with a St. Lazarus message on it," the 38-year-old Boston resident said. "I said, 'How did this come to me? Who wrote this?' It was like getting an anonymous chain letter in the mail, but a bill has a serial number, it could be tracked."

So Eskin made it his mission to start tracking the bills himself. He created an information-age parlor game out of a Web site. If you want to play, the process is simple. You mark a few bills with the Web address www.wheresgeorge.com, record their serial numbers on the Web site (it's free), then put the dollars in circulation -- in other words, spend them.

Meanwhile, other wheresgeorge.com players are on the lookout for marked bills. When they find one, they enter its serial number on the Web site. With patience and luck, you can track your marked money by computer as it travels around the country, sometimes from coast to coast. Dedicated players, known as Georgers, send thousands of bills into circulation, mark their success by the number of "hits" their bills receive, and e-mail one another with stories of dollar discoveries. It's a charming union of high-tech communication and caprice.

In the beginning, Eskin's site drew a mere handful of users a day. Now it is a certifiable pop phenomenon, with wheresgeorge T-shirts and other novelties for sale and copycat sites springing up around the world.

Despite the fact that wheresgeorge has obviously struck a chord in the collective computer-age psyche, Eskin makes no grand philosophical claims.

"I look at the stories people post all day, every day," he said. "A lot of times someone will say I found a bill in a strip club last night and someone else will say I found it in the collection plate on Sunday morning. Or you can see a bill travel from Kentucky to California and back to the same little town in Kentucky. Those are the anecdotes I tell people about. I just think it's a way to spend quality time online.

"It's just about tracking bills. It's not about making money. Nobody's exploiting the users. It's a safe haven from the big bad Internet world out there."

Ironically, Eskin admits that he's never found a wheresgeorge bill. "I'm still waiting for the magic day when I get one naturally," he said.

What began for Eskin as a lark eventually attracted the attention of the Secret Service, which asked him to stop selling rubber stamps for marking bills.

"Right off the bat they were pretty amicable," he said. "They said, 'Here's our request, you can accept or not.' I think they wanted to (make sure) that what was going on here wasn't more sinister. There's a law that says it's illegal to advertise on money, so they asked me to stop selling stamps for a profit, and I did.

"Banks were complaining. People were getting a stack of 100 dollars, stamping them, then giving them back to the bank. The bank gave them to a customer, who didn't want to take them. Then there's the occasional annoyed citizen who thinks it's blasphemy to mark a dollar and fires off an angry letter."

The law itself is tantalizingly vague. Title 18, Section 333 of the United States Code reads: "Whoever mutilates, cuts, disfigures, perforates, unites or cements together, or does any other thing to any bank bill, draft, note, or other evidence of debt issued by any national banking association, Federal Reserve Bank, or Federal Reserve System, with intent to render such item(s) unfit to be reissued, shall be fined not more than $100 or imprisoned not more than six months, or both."

Lawyers live for words like "intent."

One group of avant-garde artists (whose work can be seen at www.subnote.net) has done an end-run around the question of disfiguring money by stamping their bills with dyes that are only visible in strong ultra-violet light (sunlight, for instance), but remain hidden under other circumstances.

Most stampers, though, probably find the ever-so-slightly outlaw aspect of marking money to be part of the appeal. Marking money has the same sort of playfully subversive quality as placing crank phone calls and carving initials on an oak tree.

There is little incentive for the government to prosecute these small-time money messagers. And that's good news for people like Web site writer Michael Seery, 34, who has been collecting altered cash -- primarily bills with political slogans -- since 1998.

He has found bills labeled: IN GOD WE TRUST. KEEP ABORTION LEGAL AND SAFE. LESBIAN $$$. BISEXUAL MONEY. PAID FOR WITH TRAWLER DOLLARS (commercial fishing advocate?). WHERE IS MY DADDY? HE HAS NO RIGHTS. JEWS FOR CLINTON: ZION POWER RULES. DEO VINDICE (the motto of the Confederacy). IMPEACH BUSH! STOP STARBUCKS. FRANCE NO GOOD/FRENCH GO HOME. JOHN 3:16.

And then there was the bill with a voice balloon emerging from George Washington's lips that read, I GREW HEMP.

"The bill that got me started was the I GREW HEMP dollar," Seery said. "Every once in a while I'd find a rubber-stamp bill, but then I'd spend it. It would be the only dollar in my pocket, but then I'd have a pang of regret. After I saw the third or fourth design, I realized this was some kind of movement. So I started collecting them until I had about 12."

Seery's information-age instinct was to create a Web Site dedicated to marked dollars, which now displays 21 bills. His view of the bill-stamping phenomenon is simple.

"It's grass-roots PR campaigning," he said. "They're probably just people who don't have money to advertise. They know that bills get widely circulated. If people use dollars to spread their ideas, no matter how out-of-touch with the popular media they are and regardless of their socio-economic group, they know they'll be able to reach people randomly."

That theory certainly applies to Jme J, the 28-year-old president of the St. Louis Missouri chapter of the National Organization for the Reform of Marijuana Laws (NORML), an advocacy group promoting the legalization of pot.

J admits that he is one of the many guerrilla stampers across the country who marks dollar bills with the classic I GREW HEMP voice balloon issuing from George Washington's lips, plus a marijuana leaf on the reverse side.

"It's basically me and another person who do it," J said. "We're both pizza delivery men, so we get a lot of clean bills and we stamp them. We've been doing it for three years and we've stamped 5,000 to 6,000 dollar bills per year. It definitely enlightens people. Our founding fathers were very aware of hemp. Washington saw hemp as something good, for fiber and paper and fuel."

J recirculates the bills personally.

"I'll be at the Home Depot and I'll spend a whole stack of stamped dollars," he said. "Most of the time people don't even notice, but I know the next fifteen people in line will get I GREW HEMP bills. Sometimes a person will notice and laugh. I think it makes people more aware. In the back of their minds they might say, 'Hey, this dollar was touched by somebody who smoked marijuana.' "

J is also a Georger. He double stamps 420 bills each month with "wheresgeorge.com" and "I Grew Hemp." Why 420? J explains that 420 is a special number in stoner culture (his words), which may have been derived from the police code for a marijuana arrest, the date when LSD was invented or the optimum afternoon time to smoke.

Not everyone who alters dollar bills makes a secret of it. New York artist David Greg Harth, 27, a graduate of the prestigious Parson's School of Design, e-mails press releases announcing his latest stamping projects, most recently his REGIME CHANGE IN BAGHDAD/ REGIME CHANGE IN WASHINGTON slogan, which he began applying to bills in March.

In the past five years Harth has stamped editions of bills with the statements I AM ART, I AM GOD, I AM NOT GOD, I AM TRUST, I AM NOT A DOLLAR and I AM AMERICA. In 2001, soon after the terrorist attack on the World Trade Center, Harth, with the help of several friends, stamped I AM NOT TERRORIZED and I AM NOT AFRAID on what he says were 250,000 bills, which he intended as a defiant balm for the shaky city.

"I'm not this rich artist who has $250,000 laying around," Harth said of his stamping strategy. "I usually stamp 100 singles at a time and spend some or trade them. If I take $1,000 out of the bank and trade them, then I've got another $1,000 I can stamp. I send $1,000 to a friend in Los Angeles. I've also traded with people in London, Tokyo and Berlin.

"I'm not really for or against anything politically," Harth said of his ironic messages, "I just want to spark a dialogue. Usually when you pay for something with one of my bills, it sparks up a conversation. We need this kind of dialogue. A few friends of mine have had trouble spending my bills. People worry if they are really dollar bills. But often people would agree with the message and say, 'Do you have more?'

"There's a bar on my street where I spend money. The owner said, 'I agreed with your I AM NOT TERRORIZED money, but I'm not sure I agree with your REGIME CHANGE bills.' "

Seery, however, says there is one bill reputedly in circulation containing a sentiment with which few people would disagree:

PLEASE RETURN THIS DOLLAR IF FOUND.