More than 15 loosely organized street gangs or "youth groups" similar to the "Eighth and H Street Crew" linked to the brutal October slaying of a Northeast woman have sprung up in the city over the last 18 months, D.C. police officials say.

Known by such names as Gangster Chronicles, the Hillboys and the Enforcers, the groups are estimated to range in size from 20 to 300 and police officials say their emergence signals a significant new crime problem in the District.

"Washington has never had 'street gangs' and we don't refer to these groups as 'gangs,' " Assistant Chief of Police Marty M. Tapscott said in a recent interview. However, he said, the groups have been reported in "all quarters of the city," and "if we don't get in and nip it early, it may evolve into something."

According to one police official, fights between members of rival groups are becoming more violent and include a growing number of shootings and stabbings. "Most of the leaders are armed with handguns and have easy access to them," he said.

Many parents, school officials, business owners and civic leaders agree with Tapscott's assessment that gang activity is increasing and becoming more violent.

A tangible measure of that violence has been dramatic increases in vandalism in neighborhood near the Washington Coliseum, Third and M streets NE, where members of the groups often attend rock concerts. More than 13 storefront windows along Benning Road and H Street NE were smashed after one recent concert, and residents have reported youths leaving concerts there have vandalized automobiles and houses.

In October, police formed a special nine-member Youth Task Force, the first police unit to specialize in youth groups since the Group Activity Section was abolished in 1976. Deputy Chief Fred Thomas of the Sixth Police District said of the special unit, "If we have an upsurge of organized youth crime, I want to be on top of it."

According to Tapscott, police have not at this point identified the groups as being organized for the expressed purpose of engaging in criminal activities. Many members belong simply to be with their peers, not to commit crimes, he said.

In the case of Catherine Fuller, a mother of six who was fatally beaten about two blocks from her home, 10 suspects, all between the ages of 17 and 22, have been arrested, police said. Police said they are members of The "Eighth and H Street Crew," a group that congregates in the riot-scarred H Street Corridor, where high unemployment and a dearth of organized youth activities have left little for some residents to do but "hang out."

According to police affidavits filed in D.C. Superior Court, Fuller, 49, who lived at 923 K St. NE, was walking home from the grocery store about 6 p.m. on Oct. 1 when three men forced her into an alley that runs between Eighth and Ninth streets.

While one of the men stood lookout, the other two began beating her, the affidavits say. More men and a 17-year-old juvenile arrived "In this particular case, when you have that many people involved in a crime, a kind of mob mentality takes over," said a homicide official. from both ends of the alley and joined in the attack, after which Fuller was dragged to a vacant garage in the rear of 802 Ninth Street NE.

There, the affidavits say, Fuller was brutally kicked, stripped of her clothes and sodomized with a metal object. Afterward, the men, who numbered at least 10, took her money and jewelry and divided it among themselves before fleeing, the affidavits say.

Fuller was pronounced dead at the scene. The D.C. medical examiner ruled that she died of blunt force injuries suffered during the assault."In this particular case, when you have that many people involved in a crime, a kind of mob mentality takes over," said a homicide official. "It's possible some became involved just because they were hanging out on a corner."

In fact, many of so-called "members" of the groups are persons who simply have nothing to do and hook up with their friends for an evening, said a detective assigned to the Youth Task Force. "A lot of the people we arrest are first offenders who were just tagging along" and got misled.

Compared with Los Angeles, which has 400 gangs with a membership in excess of 30,000, or Chicago, where so far this year police have logged 60 gang-related deaths, "we're in the real minor leagues," Tapscott said.

Unlike the general stereotype, members here, who range in age from 13 to 22, don't wear jackets with insignias, don't have dues or a clubhouse, and they apparently don't have set meeting times.

Though they generally leave citizens alone, there have been a number of assaults, robberies and burglaries that have been tied to the groups, but most of the incidents involve destruction of property.

One recent incident involved an elderly woman who was involved in a "fender-bender" accident with a group member near the intersection of Third Street and Florida Avenue NE, a police official said.

"The kid jumped out of his car, got onto her hood and kicked in her windshield," he said. Other members "got riled up and punched out her other windows, assaulted her and snatched her purse."

In another incident, he said, "a whole crew busted out the window" of the High Diary Store, 1101 H St. NE, and "went in and ransacked the place."

"All our problems have been juvenile-related," said Robert Johnson, the manager of the store. "Stores all up and down the H Street corridor have the same feeling: that our problems are coming from the teen-age group."

The majority of damage has occurred after concerts at the Coliseum. About once every three weeks, nearly 6,000 people, many of whom belong to the groups, attend "go-gos" where local rock groups perform.

All the persons who attend the concerts are subjected to an aggressive "patdown" at the door by private security guards who patrol inside during the performance. Drugs, handguns, knives and brass knuckles are routinely confiscated, police say.

Not all the weapons are found, however, and there has been at least one serious shooting and several serious stabbings during performances that have been tied to feuds between groups, according to police.

Neighbors of the Coliseum have filed a slew of complaints with the police, saying that when the shows are over about 3 a.m., boisterous crowds pour out on to the streets and smash windows, break into cars and tear down fences.

About two months ago, police started adding manpower to the concerts, and now numerous police cars escort groups of teen-agers down H Street and Florida Avenue as they walk home.

Officials are uncertain why the city's teen-agers are banding together, but most say it is due to an increased sense of security and power and, on occasion, for protection from other groups.

However, Richard L. Sowell, head of Advisory Neighborhood Commission No. 11 in the Bloomingdale section of the city, traces the rise in youth groups to budget cuts in the D.C. Department of Recreation, high unemployment and a lack of job programs for the city's youths.

"Last summer, the kids had to take recreation into their own hands and they formed groups," Sowell said. "It's nice and cute when they're little kids, but when they're teen-agers, they become youth gangs. If we had organized recreation, these would be basketball teams, but because they're not supervised they're clashing heads, and people are scared as hell."

Alexis Roberson, head of the D.C. Department of Recreation, said that budget cuts are not to blame for the rise in the groups and that her department may increase the number of "roving leaders" in the city, who counsel youths and "try to change their behavior through wholesome recreation."