THE PARTY was going strong on Anthony Hillary's doorstep. Mr. Hillary, a librarian at the Petworth Library, had made an investment by buying a house near 6th and Newton Streets NW, in the Shaw area. He bought the house hoping the run-down neighborhood would soon change for the better. But on that day in 1974, the area had not changed from a poor neighborhood with its share of tough teen-agers, drunks, prostitutes and addicts. About 15 people were drinking liquor, gambling and loud-talking on his doorstep. Mr. Hillary's roommate went out and asked them to leave. They called him a white SOB and refused to leave. Mr. Hillary, a black man, came to the door. He said he was a black SOB and he wanted them to leave. Again the group refused. Mr. Hillary went in the house and came back with a rifle. He fired a barrage into the city sky. People ran helter-skelter. The party was over.

For Mr. Hillary that was the start of a huge fight. He is now the head of a vigilante group (he prefers to call it a citizens' safety patrol group) that patrols his new neighborhood in the 14th Street area with guns, dogs and sticks in search of robbers and muggers. The group was created after robberies and assaults against newcomers in the area. The robberies and the vigilante group reflect the tension in some city neighborhoods undergoing renovations. The rich and middle-class are moving in, living next to the lower-middle class and poor, sometimes pushing them out. The vigilante response is by no means limited to the city; but the tension and friction are all the more apparent and intense in the city when the newcomer is white and the neighborhood is predominantly black.

Mr. Hillary says the vigilante group was formed because the newcomers to the neighborhood had a sense of isolation, as if they were under siege. He says people have been robbed in their homes or beat up on the street. Newcomers in the 14th and Harvard streets area have met with police, seeking added protection, Mr. Hillary says, but the police have not done the job. That, he says, is why the vigilante group now walks the area.

But frustrations with the changing neighborhood are not limited to newcomers like Mr. Hillary. People who have lived in the neighborhood for years are frustrated with the crime and a constant stream of intimidating remarks. And for the people who like to sit on the stoop drinking and gambling, there is the threat of the new people coming in, changing the neighborhood, moving into houses where old friends and neighbors used to be. With the higher property taxes that come about as a result of the high prices the newcomers pay for their renovated houses, there is direct threat to some of the remaining longtime residents that they wil be the next to be pushed out.

Maurice Turner, assistant chief of police, has informed Mr. Hillary that it is illegal to carry arms, loaded or unloaded, in the city streets. And Mr. Turner has told the group that the police department does not endorse vigilante or safety patrol groups as a crime prevention technique. He is worried that other city residents, also frustrated with crime in their neighborhoods, may form similar groups.

Mr. Turner's disapproval of the vigilante group may sound like what an assistant police chief has to say publicly about a vigilante group. And to people who feel unsafe in their neighborhoods and homes, his words may sound empty. But consider what he is saying. If inexperienced people, carrying guns, patrolled the city, would you feel safer than you do now? It is doubtful.But also vigilante groups are grossly ineffective in scaring away muggers and robbers. Any bad guy who couldn't plan an attack or robbery to avoid a loud, large group of inexperienced neighborhood-safety patrollers is probably not going to be successful in breaking into a house that has even minimal security.

What vigilante groups do accomplish is to let robbers know that the neighborhood is alert to the threat of robbers and attackers. And they offer a psychological comfort to people who are fed up with being victims. But those ends can be better -- more consistently -- accomplished without the danger of armed and angry people roaming their neighborhoods dreaming of Clint Eastwood-type heroics. A neighborhood in which people watch out for each other and each other's homes (and call the police if there is any problem) is a neighborhood robbers and muggers are likely to avoid. If people in the neighborhood take the time to work consistently with police community groups and pressure police for more attention to their area, then, again, robbers will be less likely to do business in the area. If the police don't respond to demands from the residents, then meeting with their superiors or District Building officials could bring results.

Such actions take time and sustained effort. And they bring solid, long-term results -- unlike short-lived vigilante bravado that often ends when reporters and TV cameras go away. But people buying houses in changing neighborhoods must realize they are also buying neighborhoods. And if they want improvements in the neighborhoods, they will have to do more than wish and wait for other new people to buy homes in the area. For people who have lived in the neighborhoods through the years of neglect, the newcomers offer a fresh chance to organize against the muggers and robbers. The changes in the city do not have to lead to vigilante violence. They can end up making things better for everyone.