In the perpetual night of Caesars Palace, where the baccarat dealers wear velvet jackets and high rollers risk $5,000 on the turn of a card, the regulars speak in whispers about a dapper Cuban gambler who lost millions and stuck the casino with a $547,000 debt.

This gambler will not be seen again in Caesars for a long time - if ever. On Oct. 20, in a brightly lit courtroom 2,500 miles away in Brooklyn, Antonio Cruz Vazquez was sentenced to 15 years in federal prison for masterminding one of the largest retail heroin operations in the United States.

By itself, the conviction of Cruz Vazquez and his associates was significant enough. It demonstrated, for other drug dealers, the increasing efficacy of the network of surveillance and paid informants used by oft-criticized federal Drug Enforcement Agency. And it meant the end of an $18-million-a-year drug smuggling ring that annually brought an estimated 600 pounds of heroin into New York City and neighboring New Jersey.

"In my career of almost 18 years I have never seen so much money in one place . . . as I did in this trial," said Jack Mishler, presiding judge of the eastern district, after the verdict.

But the conviction of the 52-year-old Vazquez went beyond the smashing of any drug ring, no matter how important. The trial of the one-time penniless Cuban immigrant known to his friends at Caesars as "Niko," also provided a rare glimpse into the shadowland of Las Vegas where international drug dealers meet to arrange business deals, entertain women and gamble away millions of dollars in illegal drug profits.

"A lot of the big ones come to Las Vegas, both to discuss buisness and to gamble," says William Alden, head of the Las Vegas unit of the DEA. "It has a lot of anonymity. If you were to try to exchange half a million dollars even in Los Angeles it would attract the attention of everybody. In Las Vegas, they don't even look at you twice."

In addition to the anonymity, gangsters find they are treated like potentates in Las Vegas, a town where inquiring into the source of a gambler's money is considered both bad form and unhealthy.

High rollers are offered rooms, food, drinks and entertainment and sometimes feminine companionship - all on the house. And in the case of Cruz Vazquez, according to reliable reports, Caesars provided $25,000 of furnishings for his lavish Las Vegas home.

"I can't specifically confirm the figure but there is no question that substantial gifts, including furnishings, were given to Mr. Cruz," said Richard Sheehan Jr., secretary and legal counsel for Caesars World, the parent company of Caesars Palace. "We spend substantial amounts on promotion. We give out jewelry we give out automobiles."

Unlike an out-of-town high roller, whom Sheehan said might want a Mercedes or a Cadillac, Cruz Vazquez was building a house in Las Vegas and wanted furnishings. So, Caesars gave him what he wanted.

Sheehan said similar practices are followed at other casinos but the gifts are "probably more substantial" at Caesars because of the amount of business done there and its attraction for high rollers.

By almost any standard, the gifts to Cruz Vazquez were good business investments. Casinos have an unpublicized rating system in which they grade in five categories the gambling abilities of their high-rolling clients. Cruz Vazquez was ranked in a bottom grade, a judgment merited by his performance.

Caesars cage manager Donald Klinker, testifying at the trial, said that Cruz Vazquez had lost $2.9 million during a 2 1/2-year period that ended in December 1977, a month before the Cuban heroin dealer was arrested in Las Vegas.

Testimony at the trial showed that Cruz Vazquez gambled almost exclusively at Caesars Palace and spent most of his time there when he wasn't at home directing his smuggling ring by telephone.

"And he [Vazquez] also stated that his life in Vegas was restricted to travel between Caesars Palace and his home, and from his home to Caesars Palace," said Nevada narcotics investigator Jorge Fonte at the trial. "He stated, 'It seems to me that all I ever do is lose . . .'"

The name of Caesars Palace arose frequently during the federal investigation and subsequent trial. Federal authorities said that money used to purchase the drug shipments in the East was wrapped in bank wrappers from Caesars Palace. One of Cruz Vazquez's chief lieutenants in the heroin ring was Andres Rappard, a blackjack dealer at Caesars who was convicted and sentenced to five years in prison for his role in the smuggling operation.

It was no accident that Cruz Vazquez came to Caesars Palace, among the more garish and ornate of the casinos on the Las Vegas strip, to do his gambling. His buiness was solicited by Mandy Campo, a Cuban-born, naturalized citizen who was known in his native country as Armando Campillas.

Campo, named director of Latin American affairs for Caesars Palace in 1974, received adverse publicity in the Las Vegas Sun in 1975 when he was arrested for purportedly possessing a substantial amount of cocaine. The newspaper said Campo was "rumored in law enforcement cirlces to be 'Numero Uno' in the Cuban Mafia factions," a charge which Campo denounced as baseless and which the newspaper never proved.

Caesars executive Sheehan said the casino suspended Campo without pay until the indictment was dismissed several months later.

But the casino kept Campo employed this year at full pay when he was indicted and pleaded no contest to four counts of federal income tax evasion. Campo, who admitted evading tax payments of $55,000, received probation and the relatively light sentence of a $30,000 fine.

In his plea for probation, Las Vegas criminal attorney Oscar Goodman called Campo "a valuable citizen" and observed that Caesars trusted him enough to send him to South America to collet debts from casino clients.

Harry Wald, president of Casesars Palace, last week termed Campo "highly reputable." And Sheehan, referring to Campo as "a very valued employe," explained that Caesars did not fire him because "our feeling is that his income tax evasion case was totally not job-related."

Sheehan said neither Campo nor anyone else at Caesars tried to check the source of valued customers' income, although he acknowleged checks are made on a customer's ability to pay.

"We're selling product here", he said. "If a person comes in to buy an automobile, the dealer doesn't ask where his cash comes from. We think it highly inappropriate to check the private backgrounds of our customers."

Sheehan said that Caesars goes out of its way to attract Latin American and other foreign clients by having staff members who speak many languages.The casino has an office in Mexico City and Caesars also recently opened a high-class Latin American restaurant, "The Spanish Steps," to cater to its south-of-the-border clients.

"We're the most popular hotel in the United States for foreigners," Sheehan claims.

Campo has helped build that popularity in South America, where he is well-acquainted with many of the high rollers. He brought Cruz Vazques in to gamble and gave him his initial credit, although Sheehan said that higher amounts - he declined to give the specific figure - would have required approval by a credit committee of top executives.

The exact line of credit enjoyed by Cruz Vasquez at Caesars is in dispute, though the preferred status he was accorded as a high roller is freely acknowledged. Federal authorities testified that the credit line was $1 million. Klinker testified that Cruz Vasquez at one point owed Caesar as much as $689,000. Sheehan said this figure was close to the credit line of approximately $700,000.

Caesars leads the way but is not alone in paying special attention to Latin America. It is an increasing preoccupation in the Southwest in which Hispanics are by far the largest minority.

As in the above-ground world of legitimate business, there are those who feel that Latin Americans don't get enough credit for their successes in the drug trade.

"Cruz was a big, sophisticated operator," says one highly placed Vegas source. "He would have achieved a lot of fame if he had been Anglo or Italian."

Besides their growing numbers, there is an obvious reason why Latin Americans play a prominent role in narcotics dealing. Most of the hard narcotics and an increasing percentage of marijuana in the United States come from Latin America. The primary sources of supply, outside of Mexico, are Peru, Bolivia, Colombia and Jamaica.

Cuban-born smugglers like Cruz Vasquez have played an increasingly important role.

The rise of the Cubans, say officials, is similar to the success of Sicilian and Corsican mafiosi in the United States after Mussolini expelled them from Italy. Leaving Cuba for Mexico when Castro came to power, the Cubabs moved first into an alliance with the Italians and then into competition with them.

When an international drug crackdown eliminated the so-called "French connection" in 1972, the Mexican heroin sources managed by Cubans became of primary importance.One of these Cubans, a former poverty-stricken refugee named Alberto Sicilia-Falcon, became so successful that he and his four top aides took in 3.5 million weekly from U.S. drug sales which they deposited in Swiss banking accounts.

Sicilia-Falcon, who also liked to play baccarat at Caesars, was arrested by Mexican officials in 1975 and confessed to drug dealing after heavy interrogation. He is now serving time in a Mexico City prison.

Others, like Cruz Vazquez, were quick to fill the vacuum. They operated out of Miami, directing boat and plane traffic, and from Las Vegas, where the Cubans and their Mexican allies rather than the Sicilian-descended Mafia now dominate the drug traffic.

The Havana-born Cruz Vazquez was 32 years old when Fidel Castro came to power. At first, he must have welcomed the regime because he became a captain in the Cuban national police force. Then he disappeared, in an event still shrouded in mystery.

According to reports obtain by U.S. law enforcement officials, Cruz Vazquez turned up in Nicaragua where some said he was working for the U.S. Central Intelligence Agency and others claimed he represented Cuban army intelligence. When a Nevada narcotics officials questioned him about these reports after his arrest last Jan. 28, Cruz Vazquez declined to discuss them.

It is known that in the 1960s Cruz Vazquez obtained a false birth certificate showing he had been born in Puerto Rico. Over the next decade he was arrested three times, twice on drug charges, and convicted each time. In 1970, after being arrested for trying to smuggle 596 pounds of marijuana over the border at Almagordo, he was sentenced to five years in prison at Latuna Prison in Texas.

Suffering from a heart condition and with time off for good behavior, Cruz Vazquez was released from prison in 1973. Then his fortune changed for the better. Traveling to Mexico, he met and married Modesta Zambada, daughter of one of three Cuban emigre patriarchs who federal officials say dominate heroin smuggling from Mexico into the United States. By virtue of this marriage, he became a Mexican citizen.

"The Zambada family had been into drugs for years but for a long time didn't have a place to sell them," says one federal narcotics official in New York. "Then along comes Vazquez who is streetwise and marries Zambada's daughter. She's in her late 20s, he's in his 50s and old enough to be her father. It's a marriage made in heaven."

The drug smuggling operations which Cruz Vazquez directed for the next four years was both well-organized and well-greased. It originated in the Vazquez-Zambada family farm near Culiacin in the Mexican state of Sinaloa. Culiacin was a well-known drug source. The Vazquez ring shipped the heroin by air in suitcases to another destination in Mexico. There, a bribed baggage attendant working for Aero Mexico changed the baggage tags.

When the plane reached Tucson, another bribed attendant slipped the heroin-laden suitcase through customs.

There were many variations on this theme. When the air route became too difficult or dangerous, the drugs were hidden in automobile tires and transported over the border at Nogales. Bribes helped there, too. In one celebrated instance, say federal officials, a marked Mexican police commandante's car was used to smuggle the heroin over the border.

When Cruz Vazquez started out, he directed the Tucson operations in person and sometimes accompanied the Lear jet which took the contraband cargo to New York. Later, he operated strickly out of his home in Las Vegas, overseeing his operations by telephone.

His Las Vegas base apparently reflected his love for gambling and a growing conviction, experssed to officers at the time of his arrest, that his children would be the target of kidnappers in Mexico.

Throught all his profit-making and gambling losses, Cruz Vazquez impressed those he delt with as a well-mannered sophisticated gentleman who would have been equally at home in the world of legitimate business. His subordinates remained loyal to him throughout the trial. Some of them remarked on his acts of generosity, including the gifts of four automobiles to friends or employees.

On one Christmas at Lake Tahoe, with an entourage that included his two small children and various relatives, Cruz Vazquez ordered his pilot to go to a large Las Vegas toy store and buy two of every toy in the place. It took the pilot two 900-mile round trips from Vegas to Tahoe to bring in the toys.

Like other big drug smugglers, Cruz Vazquez lived high while the money was coming in and seemed to accept the idea that he would someday be caught.

"I can only make one mistake on my end of the business," he philosophically told the federal narcotics officials who arrested him at his home in Las Vegas last Jan. 28. "You fellows can make a mistake every week."

The autumn of 1978 could be said to have been a bad season for the Cuban connection - and not for Cruz Vazquez alone. First, the DEA in Miami announced the drug-related arrest of Jose Medardo Alvero-Cruz, a Cuban who was considered the "Mr. Untouchable" of south Florida. Then, Mexican police arrested Jaime Herrera, who law enforcement officials of both countries consider the chief wholesaler of heroin smuggling into the United States. Finally, Cruz Vazquez was sentenced to a 15-year term under the U.S. government's (RICO) section that does not allow for probation or parole.

All this would seem to be good news. The bad news is that there are other "untouchables" and distributors ready to take their place, and that state and federal manpower in this important drug transshipment area is relatively low.

"We have less than 30 offices and it's very difficult to stop the drug smuggling," says a Nevada state narcotics official. "More than three-fourths of Nevada is desert. You try to stop them but you don't have the manpower. You can't guard every dry lakebed in the state."

Some narcotics officials believe, however that there has been a decrease in the classic "mom and pop" marijuana flights in which a small plane from Mexico is greeted by a waiting van with windows covered on a remote airstrip. The measurement of this kind of operation, they say, is plane crashes in the desert, of which there have been very few in recent months.

What has been increasing instead, according to law enforcement sources, is the use of Las Vegas as a gambling and meeting spot for the high rolling, hard drug dealers like Cruz Vazquez, especially those who come from South America. Many of them head straight for Caesars, which, in the words of an eastern federal official who is not likely to win any civil rights award, "suits the gaudy taste" of the Cubans and their Latin associates.

"Las Vegas is fun, women and songs and no questions asked," says a high-rolling Nevada gambler who is afraid that the influx of foreign drug dealers will some day lead to a federal crackdown. "The entire culture of this community is against asking questions. When you go to a place like Caesars, the only thing they care about is whether you have money that you're willing to lose. It's the ultimate democracy." CAPTION: Picture 1, Caesars Palace, which reportedly provided Cruz Vazquez $25,000 in furnishings. UPI; Picture 2, Antonio Cruz Vazquez . . . former high roller serving 15 years