Suddenly, John Jureidini's house in the quiet Potomac Hills section of McLean started to resemble a 7-Eleven. People parked in front, ran inside for a few minutes, then left.

Police, alerted by a suspicious neighbor, filmed the comings and goings. Not long afterward, Jureidini pleaded guilty to selling cocaine.

Domingo Martinez didn't like to take his work home; he preferred parking lots.

Last September, he drove his BMW into a lot on Wisconsin Avenue in the heart of Bethesda where he met an undercover police officer. The officer says Martinez sold him $400,000 worth of cocaine. Martinez, who has maintained his innocence, is scheduled to go to trial in June.

There is virtually no neighborhood in Northern Virginia nor Montgomery and Prince George's counties where drugs have not been sold and could not now be bought, according to search warrants and police officers in those jurisdictions.

Just two years ago, police say, many suburban drug users drove to the District for drugs. They have little reason to do that today; drugs have come to them.

"Cocaine is readily available in all areas of the county," said Fairfax police Lt. William Noble. "If you know the right people, you don't have to travel from Chantilly to Route 1 to find it."

"We've made arrests in Potomac, Rockville, Germantown, Silver Spring," said Montgomery police Lt. Ron Ricucci. "If you use drugs, you're in a group that knows where the neighborhood drug dealers are."

In Washington's close-in suburbs, there are 23 identified open drug markets where buyers can drive in, roll down their car windows and purchase cocaine as they would french fries at the drive-through window of a fast-food restaurant.

In Montgomery County, an area known more for wealth than crime, there are at least nine of these public drug markets.

"If you went to an open-air market, you would see a group of men standing on the curb, flagging cars down," said Prince George's County police Lt. Clark Price. "Sometimes they are so bold they walk right in front of the car."

The drug trade in Washington's suburbs has grown so fast that it rivals the drug underworld in any other suburban area in the country, according to federal law enforcement officials and a Rand Corp. report released Thursday.

Washington's suburbs had worse drug abuse problems with cocaine and PCP than did any other suburban area nationwide in 1986, and ranked second only to Detroit's suburbs in the level of heroin use, according to the Rand report. Those rankings were based on hospital emergency admissions triggered by drug use.

Much of the suburban drug trade takes place indoors -- in living rooms, hotel rooms, bars and restaurants -- making it more difficult and time-consuming for police to penetrate.

Despite the impediments, Fairfax and Montgomery police together confiscated nearly $10 million worth of drugs last year, almost as much as the $11.4 million seized in the District, whose increasingly violent drug trade is far better known.

"It's not some dark-skinned or foreign-looking man who is selling drugs" in the suburbs, said David Harrington, a counselor and consultant to law enforcement agencies around the country. "It's the kid on the soccer team.

"Buying drugs is as easy as going to an Avon or Tupperware party."

In Prince William County, drug arrests more than quadrupled last year, from 332 in 1986 to 1,616 in 1987. Alexandria and Arlington also reported large increases in drug seizures and arrests, and Prince George's County has had an outbreak of drug-related street violence in recent months.

"People in the suburbs say, 'Why should I take a chance {getting harmed when buying drugs} near RFK {Stadium} when I can go to Fair Oaks and buy them?' " said Mario Perez, a spokesman for the federal Drug Enforcement Administration.

As the suburban drug trade has grown, so has its sophistication. Drug dealers often rotate their home base and, wary of police raids, often do not keep their drug stash and cash in the same place, officers said.

"As time goes by, they are getting more sophisticated," said Arlington police Lt. John Karinshak. "We'll be out on surveillance and following a car and find out that we are being followed.

"They use car telephones that are almost impossible to lock into {wiretap}," said Karinshak, who heads Arlington's drug investigations. "And they hide the drugs in any place imaginable."

Some of the hiding places found by police have included:Boxes of cereal. A 4-year-old's tennis shoes, while the child was wearing them. Athletic supporters. Spice racks. An oven. Behind light switches and in the gutters outside homes. In baking soda.

Suburban police say dealers generally prefer selling drugs from hotels, motels and apartment complexes because a continuing stream of brief visitors is less noticeable. But increasingly, police say, dealers are finding that some subdivisions can be attractive bases because so many homes are empty all day.

"Generally, the more experienced drug merchants use a hotel," said Alexandria police Officer Dennis P. Butler. "They don't like to stay in one place too long. Because they know there are so many informants out there, they don't let moss grow under their feet."

Last month, a maid at the Old Colony Inn just off the George Washington Memorial Parkway in Alexandria found a kilogram (2.2 pounds) of cocaine, worth about $50,000, underneath a nightstand in a room, Butler said.

Two weeks earlier, Alexandria police arrested a man in that room on drug distribution charges, according to Butler. During their search, police recovered less than one ounce of cocaine.

Other suburban drug seizures have been more fruitful: Four pounds of cocaine was found in a secret compartment in a car in Fairfax County last year. The compartment opened when two screws under the dashboard were simultaneously pressed with a piece of metal. Thirty pounds of cocaine was confiscated last May when a Hyattsville resident tried to sell $1.3 million worth of the drug to an undercover officer in the parking lot of the White Oak Shopping Center in Silver Spring. $66,000, five pounds of cocaine and 12 handguns and semiautomatic weapons were taken from a house near Fair Oaks Shopping Center in Fairfax County. Three bags of cocaine were found in the tape deck of a car stopped on I-395 near Edsall Road in Fairfax County.

Although many of the drug sales in the suburbs occur behind doors, police say there is also a growing street trade. In Alexandria and Montgomery, Arlington and Prince George's counties, almost all the open drug markets are located near lower income apartment complexes, officers say; in Fairfax, police say most street sales take place in Reston and along Rte. 1, especially in Hybla Valley.

It is in these poorer areas with open drug trafficking that police worry that the violence that often accompanies drugs will come. If gangs begin fighting over whose turf those corners are, police say, there could be considerable trouble. In the District, 35 homicides since Jan. 1 have been linked to drugs.

"The suburbs are just behind the District," said DEA investigator Kevin Tamez. "We are seizing more guns {in the suburbs} and larger quantities of drugs. Violence follows drugs."

"We are very concerned" about violence, said Arlington police Sgt. John Ice. "So far we have been lucky, but I don't know how long that will hold up."

In recent months, Fairfax police have responded to numerous shootings on Audubon Avenue in Hybla Valley, a street where police have searched at least four apartments and found bags of cocaine, cash and a .357 magnum revolver.

Around midnight on Sept. 16, police searched apartment 101 at 7980 Audubon Ave. According to the affidavit filed in Circuit Court in support of the warrants, as police entered the apartment, 23 grams of cocaine was dumped out the bedroom window. Police arrested two people on drug charges. They have not yet gone to trial.

Police officials say their best offense against the violence associated with the illegal drug trade is vigorous patrolling of open markets, yet despite stepped-up enforcement efforts, the problem does not seem to be lessening, they say.

On a recent weekday night, two undercover Montgomery narcotics investigators, accompanied by a reporter, watched as about 100 people thought to be drug dealers stood in streets or apartment hallways, waiting for customers.

As the officers drove down Scotland Drive near Rte. 270 in their unmarked car, they saw several other cars stop as youths approached.

"That's the way they do it," Sgt. Fred Fuhs said as a man in a white Ford rolled down his window and apparently took something from one youth.

Along Good Hope Drive and Briggs Chaney Road, street dealers wary of undercover police, who arrested nearly 700 people in the county on drug charges last year, scattered as the unmarked car approached. "Cops!" one youth yelled.

The officers, driving into the Summit Hills section of Silver Spring, said most of the dozen youths standing inside apartment doorways were waiting to oblige those looking for cocaine or its more affordable derivative, crack. "You should see it on Friday night," Fuhs said. "There are hundreds of people selling on the streets."

Although the visible drug trade occurs in suburbia's poorer areas, poor people are not the only ones buying, police say.

"At the street level, you find a lot of blue-collar workers buying drugs," said Montgomery narcotics investigator Ron Hardy. "Sometimes you'll see a {professional} come here, but mostly they buy it at work, at bars, at restaurants . . . . We've arrested real estate agents, lawyers, mid-level managers."

"Everyone from professional people to people who are homeless or living in public housing" is buying cocaine, said Noble from the Fairfax narcotics unit.

DEA officials and local police say that drug use is flourishing for both men and women and among all races and income levels. Those between the ages of 20 and 40 are particularly vulnerable, officials say, and although there is scant evidence to prove it, many of those who work with drug users say they believe drug use among junior and senior high school students may be declining.

Fairfax and Montgomery county schools report decreases in the number of students suspended for possessing drugs on school grounds.

In the 1981-82 school year, 455 high school students in Fairfax were suspended for having or using drugs on school grounds or during school activities. Despite a considerably larger enrollment in 1985-86, only 187 students were suspended for the same reason.

In Montgomery County, 369 students in grades 7 through 12 were arrested for drug use on school grounds in 1981-82. In 1985-86, 140 were.

A survey of 3,000 county students last year indicated that marijuana use had declined 27 percent since a similar survey in 1982, cocaine use had dropped 62 percent and heroin use had declined 75 percent, according to school spokesman Bill Henry.

"I think we are starting to get through to some of the younger people," said Lt. Ricucci from Montgomery County. "Those 20 to 35 {year olds} who came up in the drug culture are our buyers for the next 10 years, but we are not locking up many juveniles."

Edmonston, the Fairfax police captain, sees no immediate change, though: "I have a feeling drug arrests will go up this year. There is no indication that there will be a turnabout in the short term."