Miami is the Wall Street of the underground economy, the New York financial district of a $400-billion-a-year business empire that officially does not exist.

In Florida, far more money is made importing dope ($7 billion a year) then exporting citrus ($1.6 billion), and smuggling is as big a business as tourism.

But Miami's marijuana millionaires and cocaine cowboys are only a part of South Florida's flourishing off-the-books enterprise.

While the drug smugglers are using sophisticated international banking techniques to transfer funds out of the country illegally, wealthy Latins are carting in cash in suitcases, say U.S. Customs officials.

The banks along Brickell Boulevard now hold billions of dollars of "flight capital" that has been sent north to protect it from unchecked inflation and unstable politics of El Salvador, Colombia, Brazil and elsewhere.

Stashing cash in Miami violates the currency laws of many Central and South American nations that prohibit their citizens from draining profits out of the country or maintaining foreign bank accounts. It is underground money, but so long as it is declared to Customs, bringing it into Florida is not illegal.

While the Latin rich bring their money to Miami, the poor simply show up on its doorstep. An estimated 200,000 illegal aliens are believed to live in the Miami area. Many have found jobs in sweat shops and service businesses that don't quibble about the lack of Immigration and Naturalization Service "green card" or Social Security number.

All this underground economic activity adds up to at least $11 billion a year in Miami surrounding Date County, estimates Dr. Jan Luytjes, an economist at Florida International University and the resident expert on off-the-books business.

Luytjes calculates the underground economy accounts for roughly one-third of the area's total output, a far greater share than anywhere else in the country.

He is outraged by the suggestion of some Miami politicians that drug money is good for the city because it provides jobs, cash and prosperity.

Illegal aliens steal the jobs of black citizens, Luytjes argues. Criminals not only steal, they force their victims to waste millions a year shrouding their windows with bars and arming themselves. Guns, bars and security guards are not productive expenditures, the economist notes.

Underground entrepreneurs also undermine the development of Miami's economy, he contends. Illegal firms compete unfairly with legitimate businesses; they evade taxes, ignore licensing requirements, pay workers less than the minimum wage, and thus can charge lower prices than above-ground firms.

Underground money and undocumented immigrants "impacts the quality of life down here more than anything else," says William Rosenblatt, chief of the investigations division of the U.S. Customs Service in Miami.

Flouting of the law by smugglers and illegal aliens leads others to ignore the rules. Under-the-table payments are now showing up in real estate transactions, documented by selling prices that appear to be much lower than the going rate. A house in a neighborhood of $150,000 homes may sell for $130,000 -- after the owner gets $20,000 in cash.The phony selling price means a lower property tax assessment for the buyer, tax-free cash for the seller, and lower settlement costs for both.

Last week nine Dade County homicide detectives were indicted for stealing drugs and money and taking payoffs from dealers. Said police director Bobby L. Jones, "You are going to have kinds of situations when you have this kind of money moving into the community. It's not just the police. You have had attorneys arrested, doctors and businessmen. We are seeing the end product of what narcotics is doing to this town."

"It's eroding the very glue that holds together the fabric of this society," agreed a federal lawman who insists on anonymity. His agency wants him to keep a low profile, and he doesn't argue. In almost 20 years of law enforcement, Miami is the only place he's ever worked where federal officials' lives are threatened routinely.

It's not drug use that's the problem in Florida -- though that is rampant, too -- it's drug business, the biggest underground industry in the United States.

The Drug Enforcement Administration valued illegal drug traffic in the United States last year at somewhere between $69.2 billion and $90 billion. Cocaine imports were in the range of 40 to 48 tons, worth $26.8 to $32.2 billion. Consumption of marijmuana was somewhere between 10,600 tons and 15,500 tons; when finally sold by the ounce that much pot would bring $19 billion to $27.5 billion.

Florida's drug smuggling supplied 70 percent of all the marijuana and cocaine consumed in the United States last year, the DEA says. Texas and California also have flourishing drug-smuggling systems, and California is developing a homegrown marijuana industry, but no other state can match Florida's drug economy.

The DEA figures that Florida "dopers" took in $7 billion to $10 billion last year, accounting for two-thirds of that state's underground economy, or as it is sometimes called "the unobserved sector of the economy."

Of course, they don't often call it that in Florida, because what's going on is too obvious not to see.

The Federal Reserve Bank first noticed the influx of drug money several years ago when it discovered that all the cash in the country seemed to be draining into Florida. Other parts of the United States often ran short of currency, but the Federal Reserve Bank of Miami was accumulating cash surpluses of four or five times its normal needs.

That's because drugs are almost totally a cash business, DEA officials say. The two $20 dollar bills that a Washingtonian pays for an ounce of pot, get passed up the line from the small-time dealer to the wholesaler and eventually to the Florida connection, where marijuana deals are usually done by the ton and the cash comes in suitcases.

The multi-billion-dollar industry has long since outgrown the days when an adventurous hippy or greedy yachtsman would pick up a few kilograms of coke or bales of pot in Colombia and try to slip it into the country.

Now there are transportation networks, distribution systems, "dope brokers" to arrange the deals and "money brokers" to transfer and launder the funds, says Customs investigator Rosenblatt. "It's a business, and just like any other business, they've got their production people and their distribution and their comptrollers."

Cayman Island tax havens, Bahamian banks, secret Swiss accounts and international electronic funds transfers are used as routinely by dope dealers as by other multinational enterprises.

Because cutting the flow of contraband that's counted in the thousands of tons has proved impossible, federal authorities now are concentrating on the money.

Their chief weapons are no longer fast boats and surveillance flights, but a pair of Treasury Department forms known as 4789 and 4790.

"The drug smugglers are afraid of these two pieces of paper," says Bill Meglin, director of the Currency Investigators Division of the Customs Service in Washington.

Anyone who takes more than $5,000 in cash into or out of the country is required by law to file form 4790, declaring the money. Anyone but a regular customer -- like a supermarket -- depositing more than $10,000 cash in a financial institution must file the other declaration.

Failure to file can be no more than a misdemeanor. A Latin tourist who comes through Customs in Miami with a suitcase full of undeclared cash often won't be charged at all, because authorities know there are legitimate political and economic reasons for flight capital.

But if federal authorities can link the money to drugs or other crime, failure to file the form is a felony; the feds can seize the cash and send the owner to jail.

Use of the bank disclosure forms to go after underground cash has been pioneered by Operation Greenback, a Miami task force comprised of the DEA, Customs and the Internal Revenue Service under direction of the Justice Department.

Greenback operatives say many Miami banks have winked at the disclosure laws when offered accounts that promised to bring in huge deposits at a time when competition for funds was fierce.

The Greenback agents are pursuing dozens of drug financiers. Their biggest catch so far is a Miami businessman names Issac Kattan, who was convicted recently on series of drug and money charges.

Kattan's downfall began when, like many savers, he decided to put his cash into a money market fund so he could collect the highest possible interest. When the unassuming businessman deposited $38 million to his account in les than two months, officials of Donaldson, Lufkin Jenrette Services Corp. called the police. Even in Miami, that was too much underground cash to overlook.