During the last five years, dozens of profitable businesses that channel U.S. dollars to El Salvador have sprung up in major United States cities with large concentrations of Salvadorans.

These "transfer houses," with such catchy names as Giant Express and El Rapidito, relay U.S. funds from Salvadorans living here to their relatives in El Salvador, and operate like express mail services.

About two years ago, concern over the amount of money pouring into El Salvador but bypassing the country's nationalized banking system caused Salvadoran government banks to open their own transfer houses in Los Angeles, New York, Miami and Houston, officials said.

Ernesto Rivas Gallont, El Salvador's ambassador to the United States, said, "Most of the dollars were not coming into {El Salvador} but staying in the United States or on the black market, and the country was not benefiting but individuals were."

The transfer businesses work like this: For a fee of about $10 or a percentage of the amount being sent, the businesses will guarantee that the money will reach its recipient usually within three to 10 days.

In El Salvador, the money is delivered in dollars, colones or, more commonly, a money order that a person can later exchange for colones on the black market.

Some businesses offer 24-hour service and deliver the funds to the relative's doorstep, usually charging 10 to 14 percent of the amount being sent.

Many of the businesses offer return receipts as proof that the money has been delivered.

One company, Giant Express, with several offices in El Salvador and the United States, including one in Alexandria, has Salvadorans here mail their letters and money orders to an address in Miami. From there a company employee personally takes them to El Salvador.

The company has a radio program in San Miguel that broadcasts every morning the names of people who have received letters from the United States. Those people then go to Giant's office in San Miguel and, after showing some identification, pick up the letters. The U.S. relative pays $10 for this service.

More commonly, there are offices throughout El Salvador where the money is sent, and a U.S. relative will then telephone or telegraph the relative in El Salvador with instructions on where to pick up the money.

The transfer businesses have become increasingly popular methods of forwarding funds to El Salvador since the early 1980s when Salvadorans lost faith in the Salvadoran postal system. Two top postal officials in El Salvador were indicted then for stealing more than $1 million in money orders from letters sent from this country.

The transfer houses also are less expensive, more reliable and more convenient than wiring money from a U.S. bank to a Salvadoran bank. One local bank charges $50 for the service.

Another large bank requires the person sending money to El Salvador to have a bank account in the country. Another local bank charges $40 to wire money to El Salvador, but a bank employee said that half of the time the money does not get there.

Western Union charges $57 for wiring $500 to a bank in San Salvador.

The transfer houses set up by the Salvadoran banks have had limited success, mainly because in El Salvador they cash the money at the official exchange rate of five colones to the dollar, officials said.

But a Salvadoran who receives money through a private transfer operation can exchange the dollars in El Salvador at a higher black market rate of up to 5.50 colones per dollar, officials said.Carmen Chapin of The Washington Post news library contributed to this report.