Shereker Wilkins died on her ninth birthday last month, killed by a stray bullet fired from the street as she sat in her Milwaukee apartment, combing her mother's hair. In New Orleans the same week, Dorothy Mae Gourrier, 59, was killed on her way to a doctor's appointment. A would-be robber opened fire on her car, shattering the windshield and wounding her in the shoulder and chest.

For the last several years, law enforcement authorities have blamed drug trafficking -- especially of cocaine and its derivative crack -- for the surge in urban crime. But this year, a new and in some ways more alarming trend is developing: The drug epidemic in many American cities shows signs of abating, but the culture of violence that accompanies it is thriving as never before. After increasing steadily for three years, the number of homicides in 1990 is breaking records in urban areas nationwide.

Cocaine and crack may have encouraged and financed the violence as traffickers bought large numbers of top-of-the-line weapons to replace the cheap, poorly made "Saturday night specials" and rubber-band-powered zip guns of the past. But the ethic of firepower has taken on a life of its own. Guns have become part of the urban landscape, injecting an extra element of fear into everyday life.

"There's a viciousness out there on the street with people with weapons," said New Orleans Police Superintendent Warren G. Woodfork. "They don't care if they live or die, it seems, or if you live or die."

In interviews in 16 cities across the United States, Washington Post reporters and special correspondents spoke to law officers, community activists, criminologists, young people and residents of some of the nation's toughest neighborhoods.

In 15 of the cities, homicide rates have increased over 1989 -- Boston by 45 percent; Denver 29 percent; Chicago, Dallas and New Orleans more than 20 percent each; Los Angeles 16 percent; and New York 11 percent. In the District, which led the nation in number of homicides per capita last year, the rate is slightly ahead of last year's record pace.

Those interviewed mentioned drugs, poverty, television violence, social tension and hopelessness -- root causes of violence that have afflicted the inner cities for generations. But they also spoke of guns, gangs and a new street ethic that in many cases almost requires young men to commit murder to prove manhood.

"As kids under 18 got involved in drug dealing, they got armed," said Lawrence W. Sherman, president of the Crime Control Institute, a Washington-based think tank. "Even if drug dealing declines, they still have the guns. Once the guns have been stockpiled, you can expect they will be used in all kinds of disputes."

Gang members, said Dan Cabrera, special senior agent for the Los Angeles office of the Bureau of Alcohol, Tobacco and Firearms, "rule by fear -- fear of dying is a strong motivator. If you're trying to get respect and you've killed three or four people, people are going to jump when you give an order."

This year, the new ethic of violence has meant banner headlines for a flood of seemingly senseless, gruesome crimes -- the Wilkins and Gourrier killings, the shooting death of a 33-year-old television executive making a telephone call outside his Greenwich Village apartment, the slaying of a 21-year-old Tulane University honor student as she strolled to a bus stop on her way to work.

Even more disturbing for law enforcement, however, has been the increasing use of firearms as the preferred tool for settling disputes from domestic quarrels to schoolyard slights.

In a South Philadelphia apartment this month, Tuan Anh Nguyen, 18, was fatally shot in the chest, arm and stomach when a dance-party quarrel erupted in gunfire. In Brooklyn last month, barber Ferdinand Augustin died when a would-be customer shot him in the head with a .25-caliber pistol after Augustin refused to give him a haircut. In Chicago on one September weekend, 75 people were shot. Of those, 13 died, including Aaron Martinez, 15, an aspiring Olympic boxer shot in the face by a 19-year-old whom he had beaten in a fistfight.

"I see a lot of violence at the slightest provocation -- 'you stepped on my sneakers, you said something about my mother,' " said Mel Grizer, executive director of the United Community Center in the East New York section of Brooklyn. "There's a lot of kids getting killed over girlfriends."

There is little argument that drug trafficking has played a crucial role in spawning the rise of violent crime -- cocaine in the early 1980s and crack in the last five years. "In the 1960s and '70s, it was heroin, which just makes people lie down and go to sleep," said Richard Bank, a 17-year career public defender in the Philadelphia court system. "Today, the heroin is cocaine, which makes people very excited and nervous. They're much more dangerous."

But most available indicators suggest that, over the last year, even hard-core cocaine and crack abuse has begun to decline in many parts of the country. The number of people being treated for cocaine-related hospital emergencies peaked nationwide at 11,285 in mid-1989. During the first three months of this year, the figure had dropped to 8,135, lowest since 1987.

At the same time, the number of people arrested who test positive for cocaine appears to be declining. In the District, inmate urinalysis last July showed 17 percent of juvenile defenders testing positive, down from 35 percent in 1987. For adults, results were almost as pronounced -- 52 percent tested positive last June, down from 72 percent in 1987.

Statistics available in many other cities have shown slight downward trends, or at least a leveling-off from previous increases in drug use. By contrast, however, the Senate Judiciary Committee projected in August that 23,220 people would be murdered nationally this year, making 1990 the bloodiest on record, although the homicide rate relative to population would still be slightly below that of 1980, when 23,040 people were slain.

"Police are telling us there is more violence that doesn't involve drugs," said Stephen E. Rickman, director of statistical analysis for the office of Criminal Justice Plans and Analysis here. "It's kind of a spillover effect. It's become an acceptable way of settling disputes."

Still, many law enforcement officers do not believe that drug violence is declining. They have noticed, and the Drug Enforcement Administration reported this summer, that cocaine prices have risen over the last year while street purity of the drug has declined, indicating that cocaine is becoming more difficult to obtain.

Many law enforcement officials suggested that a relative scarcity may be fueling the upsurge in violent crime: "Now, with a shrinking market, they have to compete aggressively," Rickman said. "That sparks a certain level of violence."

And no one interviewed disputed the proliferation of guns on America's streets and the willingness of people to use them. Today's street weapon is more sophisticated, more expensive and more deadly than ever.

"They're not using 'Saturday night specials' anymore," said Capt. Donald Curole, chief of homicide for the New Orleans Police Department. "It's MAC-10s and . . . 9 millimeter" semi-automatic pistols. "Ten years ago, a victim would have one or two gunshot wounds at the most. Now you're seeing multiple gunshot wounds -- 10 to 15 in one victim. . . . There's a tremendous amount of overkill."

Boston Deputy Police Superintendent William Celester said the very availability of guns has changed the nature of street warfare. "I was born and raised in Roxbury," he said, referring to a tough Boston neighborhood. "I was a member of a gang. There were guns, but nothing like this."

In his day, Celester said, youths fought with fists, chains, bats or, rarely, knives. "So you go away with a broken arm, or maybe you got stabbed." he said. "Now you're dead, or maimed for life. Plus, these kids are quicker to fight now. They pull out a gun and BOOM!"

In San Diego, gun seizures have soared from an annual average of 1,700 in 1980-85 to 2,500 from 1986 to 1988 and about 4,000 last year. Mona Vallon, property-evidence manager for the San Diego Police Department, said she gets "carts-full on a daily basis."

"It used to be that they'd go into a house and seize one or maybe two guns," she said. "Now, they're seizing arsenals -- 10, 15, 20 guns."

The department has filled one gun room, Vallon said, and opened a second while seeking innovative ways to get rid of the swelling inventory. Traditionally, San Diego police have dumped guns in the Pacific Ocean -- 525 in 1980 but 3,000 projected for this year. The department would like to shred them for scrap but cannot find an adequate facility.

Besides more and better guns, today's violence has other prominent characteristics. One is race. In Boston, the proportion of black homicide victims rose from 41 percent in 1973 to 67 percent this year, and this year Boston police reported that 78 percent of murder suspects are black.

In New Orleans, 203 of 229 homicide victims through Sept. 30 this year were black, 187 of the black victims were male and 266 of 284 murder suspects were black. "Mostly, it is black males who are dying," said New Orleans police spokeswoman Carmine Menchel. "We're seeing black males killing black males."

Early this summer, New Orleans Superintendent Woodfork, who is black, chastised city residents for not paying attention to the city's rising homicide rate. Later, he told The Washington Post that his entreaty was largely ignored until Tulane coed Karen Lynn Knupp, who was white, was killed at a city bus stop in July.

A second characteristic of murder in the 1990s is that it involves young people more than ever. A study by Washington's Center to Prevent Handgun Violence found that the number of youths killed by firearms nearly doubled between 1984 and 1990 from 962 to 1,897.

Yet while the rate of arrests of teenagers for murder also doubled, arrests for other crimes -- including rape and robbery -- did not increase significantly, the Crime Control Institute study showed. "It's not like kids are going out and attacking more people like you and me," said the Institute's Sherman. "They are shooting each other."

That means that young people are growing up in an increasingly violent atmosphere.

At the Desire public housing project in New Orleans, one of the city's worst, 16 residents have been slain this year. Random shots echo through the neighborhood "every two or three hours," said Barbara Price, whose niece was wounded by a stray bullet on her way to the grocery store last month.

Price, a quiet, soft-spoken mother of seven, ticked off the weapons she sees regularly in Desire: semi-automatic "Uzis, AK-47s, Tech 9s" and even a machine gun or two. "A lot of these kids, they're not into drugs, they're just fascinated with guns," she said.

Carl Bell, a University of Illinois psychiatrist, recently completed a study for Chicago's Mental Health Council that found that 74 percent of 1,000 South Side and Southwest Side children had witnessed a killing, shooting or robbery. Among students from South Side high-crime areas, 24 percent had seen someone killed.

"If you're a victim of violence, you come from a broken home, you're poor . . . and if you've been knocked upside the head a couple of times, then you might think about getting a weapon," Bell said. "It is going to be a whole lot more difficult to teach a kid not to carry a gun when he's been jumped on."

Many youths congregate in gangs because they know nothing else. "They think the world is one long ghetto from sea to shining sea," said public defender Bank in Philadelphia. "They think that everybody lives like they do."

The idea is to survive and prosper in a hostile environment. Power comes from the gang or from the barrel of a gun. "It adds to the machismo," said Lt. Bruce Meyer of the Los Angeles Police Department's gang unit. A gang member willing to commit a gun crime is "sometimes looked up to by other members."

For small children, coping with the violence has become a traumatic burden. "I stay in the house almost all the time," said Malika Mitchell, 10, who lives in Brooklyn's Brownsville section and was interviewed at an East New York community center. Just two or three years ago, she said, "I would go outside and ride my bike. Now it just sits in the corner."

Jeffrey Jones, 10, had another solution: "I want to move to Florida, to Orlando. Every time I visit, when you're watching the news, you don't hear things like, 'He got shot, he's going to jail. He's on America's Most Wanted.' "

Gugliotta reported on Baltimore and Philadelphia; Isikoff reported from New Orleans. Contributing to this report were staff writer Gabriel Escobar (Washington) and special correspondents Christopher B. Daly (Boston), Laurie Goodstein (New York), Elizabeth Hudson (Dallas, Denver), Lauren Ina (Chicago, Detroit), Jon Leinwand (Atlanta, Miami) and Jill Walker (Los Angeles, San Diego, San Francisco, Seattle).