The cocaine deals at Manny's, a popular nightspot on Rockville Pike in Montgomery County, began in earnest one recent Saturday just after 11 p.m.

Under cover of the Apex band's version of "Let's Dance," a young well-dressed couple negotiated with a woman at the bar for a small quantity of cocaine. They plopped down $50 and awaited its arrival. The woman made her delivery within 40 minutes. Beside them, a 27-year-old telephone company worker named Bill spent $25, his last cash, to buy cocaine from a high school buddy named Doug. About midnight, the two went out to Bill's van, parked in Manny's parking lot, and snorted the cocaine as a guard ambled past them.

The incidents two weeks ago at Manny's surprised owner Emanuel (Manny) Alahouzos when they were brought to his attention. Alahouzos said he tolerates no drugs on his property. But, he added, drug sales "go on everywhere. We patrol it and screen it as best we can."

Other club owners in Montgomery say the same thing, but their efforts and those of local law enforcement agencies have done little to stem what police describe as a staggering cocaine trade unrivaled by other jurisdictions in the Washington suburbs. Cocaine trafficking, concentrated chiefly along a 10-mile stretch of Rockville Pike and often conducted openly in the bars and nightclubs that dot the major highway, is worsening, law enforcement authorities and other experts say.

"You can walk into any cocktail lounge in Montgomery County on a Friday or Saturday night and 'score' cocaine," declared Montgomery police Sgt. Ronald A. Ricucci, a veteran vice officer. "There's so much coke coming into the county now, bang, bang, bang."

His colleague, Sgt. Donald E. Mates, agreed. "If you look at the broad problem of cocaine, we're not having any impact," Mates said.

When it comes to cocaine, Montgomery's reputation as one of the most affluent jurisdictions in the country is also its curse, say Ricucci and others. The county's increasingly wealthy and mobile population, its location at the hub of an interstate highway network and its growing number of fashionable nightclubs and flourishing hotels have helped fuel a nearly four-fold increase in cocaine-related arrests since 1980, authorities said.

"There's plenty of money in this county, so you get the status bit with cocaine," said Sandy Clunies, who for 13 years has run Seneca House, a treatment center in Potomac for abusers of cocaine and other drugs.

Montgomery's "yuppies, they're into cocaine," she said. "It has more status than beer or pot. It's the glamour-glitter-glitz drug."

Cocaine, which stimulates the brain and increases the user's heart rate and body temperature, can have powerful neurological effects. Large doses of the drug can suppress the respiratory system and kill the user. Medical experts disagree whether cocaine is addictive, but some drug abuse counselors who have worked with heavy users are convinced that a severe dependency is tantamount to an addiction.

In many ways, the brisk cocaine trade in Montgomery is but one ripple in a nationwide tide of cocaine that the Justice Department said has "saturated the U.S. drug market."

A study prepared last month by the federal Drug Enforcement Administration concluded that recent record cocaine production in South America will help keep Miami and South Florida, southern California and New York City as the premier locations in the country for cocaine importing, processing, distribution and use.

The drug has devastating nationwide effects, the DEA warned. The agency predicts that the number of cocaine-related injuries and deaths, which last year jumped 11 and 25 percent, respectively, will continue to rise through this year, largely because of the growing popularity of "freebasing" (a technique for smoking nearly pure cocaine) and other "extremely toxic" and dangerous forms of use.

Some local experts already detect widespread problems associated with cocaine. "We're at an epidemic level with cocaine," said Richard L. Hamilton, director of the Maryland Drug Abuse Administration. At 55 state-funded drug treatment centers overseen by the state agency, the number of patients with grave cocaine problems has more than doubled in two years to 3,632 so far this year, he said.

Hamilton added that about 75 percent of those patients live in the suburbs between Washington and Baltimore, an area where he estimates 30,000 people have had their lives "seriously disrupted" by cocaine. Baltimore County, which according to County Executive Donald P. Hutchinson has "a significant cocaine problem," began a cocaine prevention program and hot line this month to combat cocaine use.

Area police departments said their success with cocaine-related arrests indicates just how quickly cocaine's popularity is rising. As police Sgt. Mates, who recently left the Montgomery narcotics squad after a three-year tour of duty, put it, "A big reason why our arrest numbers are up is because economic times are better and people are spending more money on cocaine. There's just more of it out here."

Prince George's County police said they have seized a little more than $1 million worth of cocaine this year, more than twice the amount seized last year.

"Today, we're making seizures that were nonexistent a couple of years ago, shipments of cocaine that have come here directly from South America," said Lt. Al A. MacDonald, commander of the department's vice unit. "Before, we'd seize an ounce. Now we're seizing pounds and kilos."

In the past 18 months, as the wholesale price of cocaine fell and its average purity on the street remained relatively high, the drug has spread to middle- and even lower-income groups in the county, MacDonald said.

Cocaine is increasingly popular among women. Montgomery police, for instance, so far this year have arrested 28 women on cocaine-related charges, or four times as many as they did in all of 1980.

"Coke has permeated the populace," said Mates.

Because police record-keeping varies from county to county, it is difficult to gauge precisely how many area residents use cocaine. But official statistics do indicate that cocaine use is widespread and increasing. In the District, arrests for the sale or manufacture of cocaine and similar drugs almost doubled from 1982 to 1983, from 1,031 to 1,976. In Arlington County, police report an average of 17 cocaine-related arrests per month, up from 10 per month in 1982, a department spokesman said.

Meanwhile, Fairfax County police said that each year for the past five, cocaine has accounted for about 10 percent of all narcotics arrests.

In Montgomery, arrests for cocaine sales or possession constitute a dramatically higher proportion of all drug arrests, according to police records. Between January and August of this year, for instance, there were 133 cocaine-related arrests, a rate nearly twice that in Fairfax, a similarly affluent county.

Most of the roughly $1 million worth of cocaine seized in Montgomery this year originated in South America and made its way into this country via Miami or other East Coast cities such as Washington and Baltimore, police said.

Once they arrive in Maryland or the District, large quantities of cocaine typically are cut into smaller and smaller portions for sale on the street. Some of it will be sold to heavy users, but most will be bought by casual or "recreational" users who, police said, have little fear of investigation or arrest because of constraints on police manpower and money.

Instead, Montgomery police pursue suspected dealers, such as those alleged dealers charged last month in what Ricucci termed three "significant" arrests. In 13 days, police seized a total of nearly two pounds of cocaine at a Gaithersburg restaurant and at homes in Rockville and Wheaton. In addition to the cocaine, which had an estimated wholesale value of at least $60,000, $41,000 in cash was seized. Seven persons, including two Miami residents, were arrested. All three cases are pending.

Despite such successes, many police officers, including veterans of the county's narcotics unit, are pessimistic about their chances of quashing the local cocaine trade.

"Police departments react to public outrage, but where's the outcry over cocaine?" asked Mates. "People know that dealing coke is an easy way to make money with minimum risk and a minimum chance of going to jail."

In part, the risk is low because people can be inconspicuous in the places where cocaine frequently is bought and sold: noisy, crowded bars, hotel parking lots, and busy public restrooms.

The men's restroom at Raffles II, a popular discotheque at the Marriott Hotel in Gaithersburg, which draws an affluent crowd of high-tech executives and residents of nearby Montgomery Village, was the scene of one apparent cocaine sale around midnight on a recent Saturday. A middle-aged man -- obviously nervous but trying to appear nonchalant -- handed cash to a companion, who with a gesture as casual as a handshake, passed him a small foil packet smaller than a matchbook.

The transaction lasted 10 seconds.

Marriott spokesman Jack Burk said the motel chain has a stringent policy against drug sales on its premises. But he noted that Raffles is "a place where people come in and go out. All kinds of things happen in hotels."

Michael P. Roddy, general manager of the Gaithersburg Marriott, said he has witnessed no cocaine or other drug dealing in his 14 months on the job. Both Marriott security police and "plainsclothes county police who are known to us come into" Raffles, but no drug arrests have been made in or near the lounge, Roddy said.

Manny Alahouzos said he knows that Montgomery narcotics officers patrol his nightclub, which is on Rockville Pike across from swank White Flint Mall and just north of the elite Georgetown Preparatory School. At the club, where live bands draw a young crowd from throughout the Washington area, undercover police "are welcome day or night," Alahouzos said.

"This drug thing has gotten out of hand," added Alahouzos, who opened the club 11 years ago. "But you do it here and, boom, you never come back." Several people have been permanently banned from Manny's for using or dealing cocaine and other drugs there, Alahouzos said.

Despite Alahouzos' strict policy, it was easy for Bill to obtain cocaine at the club two weeks ago. He merely offered $25 to his friend Doug for the 1/4 gram and waited 15 minutes while Doug left the nightclub and procured it.

When Doug returned, he found Bill at the bar and brushed against him, leaving a small packet of cocaine in Bill's left hand. The two then went to the parking lot and snorted it through a short plastic tube. Bill, a Montgomery native, said Manny's is one of his favorite clubs. He has bought cocaine there on several occasions, he added.

Bill was at Manny's again the next Saturday, devoting most of his time and attention to the crowd dancing to the music of a band called Motion. Again that night, at least one other apparent cocaine deal was made, this one in Manny's parking lot, involving three men who exchanged cash for a small plastic packet of white powder.

At Chasers, a posh club at the year-old Holiday Inn Crowne Plaza on Rockville Pike, owner Alan Margolius said his security staff does "a pretty good job" of preventing drug deals among customers. "I have yet to walk into the bathroom to see anybody partaking of drugs , but that's what they do," Margolius said.

"Almost wherever you go there is that influence out there," Margolius added, referring to cocaine. But "we do not want that in our hotel. It scares me to death."

Some users, however, revel in it. "There is definitely something special to cocaine," said one Gaithersburg man, who described himself as an infrequent cocaine user but who, experts said, is typical of a growing number of middle-class Montgomery residents who have tried the drug at least once.

The man, 26, who would not give even his first name for this story, earns slightly more than $20,000 a year as a midlevel employe at an accounting firm in Rockville. He said he first tried cocaine two years ago during the high-pressure income-tax season that lasts from January to April.

"We were working 12 and 14 hours a day, six and seven days a week," the man said in an interview. "I walk into the bathroom and this guy says 'Hey, is that you?' When I told him I was alone, he passed over his credit card with a line of coke on it."

The man said he used cocaine throughout the 1982 tax season and again during those months last year, tapering off during the rest of the year.

"Coke gives you a great feeling, power, control," he added. "It gets you up. You feel like you can do anything."

David, 39, a successful Wheaton businessman who said he kicked a $5,000-a-week cocaine habit last year, said he and other users would "chase the high" with successively larger doses of cocaine. Toward the end of his 10-year dependency on cocaine and alcohol, David was freebasing in places as diverse as the restroom of an airplane and outside a Narcotics Anonymous meeting in Bethesda. Once he bought cocaine in the parking lot of his neighborhood 7-Eleven store, he said.

"With cocaine, the life style becomes as addictive as the drug itself," David said. "After a while you forget about everything except your need for more coke."

Sandy Clunies, whose 28-day program at Seneca House David attended, perceives a "very permissive attitude toward cocaine" in Montgomery and elsewhere in the area. "There's nothing very subversive about it, no sneaking around for a secret phone booth to make a deal," she said. "For those who can afford it, cocaine is the drug of choice."