The three dudes from Anacostia were driving along 12th Street downtown looking for a little action on a cold Saturday night. Suddenly they heard desparate cries from a young man struggling with an assailant near Pennsylvania Avenue.

The man was being robbed. His wife, who had been robbed at knifepoint by another man moments earlier, stood on the sidewalk, tears streaming down her face. Quickly, the three Anacostians -- Vasco Anderson, 22; Eugene Connelly, 17 and Gregory Parker, 15 -- made their decision: Anderson gunned his car up onto the sidewalk, aiming it at the assailant. He missed. The three leaped from the car, grabbed one man and chased the second away. Police arrived and arrested the suspect, finding a knife and straight razor.

Call them good samaritans. Calla them fools. Call them what you want, but the three young men from Anacostia are among a startling number of ordinary citizens who police say have intervened recently in street crimes, coming to the aid of fellow citizens and, in at least one case, a beleagured police officer. Police officials are quick to say that such reports of citizen asssistance are random and do not indicate a trend. Nevertheless, the reports are heartening, officials say, especially in light of the city's skyrocketing crime.

In the first two months of this year alone, more than a dozen bystanders aided police and crime victims with various heroics:

A woman being raped in an alley near Howard University was rescued after two teen-aged boys summoned police upon hearing her screams. A suspect was arrested on the scene.

A cusotmer at the Holly Farms carryout at North Capitol Street and Riggs Road NE wrestled with a gunman who had stabbed and shot a 61-year-old security guard there. When police arrived, the customer was still holding onto the gunman who had bitten him on the ear.

Two Southeast residents, noticing at least two persons engaged in what police called "suspicious activity" at a neighbor's home, called police. When they arrived, the suspects had already fled but the residents gave police descriptions and a license tag number that led to an arrest later that day.

A teller whose downtown bank had just been robbed followed the robber outside along the street, then hailed a police officer who arrested the suspect.

But the case that amazed police the most involved two men who helped a 3rd District police officer who was being mauled by a man he was trying to arrest for purse snatching on a recent Sunday morning.

Officer Tom Yates had chased the purse snatcher into an alley near 14th and Girard streets NW, where the fight ensued. The suspect fought back, slugging Yates in the stomach. The officer doubled over in pain. His breath came in hard, jerky puffs, Yates recalled. A small crowd had formed nearby. In desperation, Yates screamed for help: "Police officer in trouble!"

As if on signal, Yates said, two men sprang from the crowd. One grabbed his handcuffs, the other knocked down the suspect and helped handcuff and place him in the back seat of the police car. Then, as mysteriously as they had appeared, the pair as well as the other onlookers drifted away, leaving Yates to pick up the service revolver he'd lost in the fracas and walk stiffly to his squad car to radio for help. He learned later that several citizens had already called for police.

Yates, a white officer, was rescued by two black citizens in the heart of the 14th Street riot corridor, an area not known for its cordiality to police. t

Yates says, however, that his recent scrape is not the first time blacks have come to his aid. "But not to this extent," he said in his buttermilk-thick Southern accent. "These guys knew exactly what to do. If i hadn't gotten that kind of help, it could have been another situation altogether.

"I have confidence in the people," he continued. ". . . People are tired of crime. Citizens everywhere are just getting fed up."

Ronald E. Crytzer, a 20-year police veteran and commander of the police department's robbery squad until he was promoted recently to night inspector, expressed a similar view.

"The people are becoming intolerant of crime," he said. "It crosses racial barriers, economic barriers, social barriers. The people are coming forward."

One who came forward, Anderson, reflected on the night of the 12th Street robbery downtown. His main fear, he said, was that he would get a ticket for parking his car on the sidewalk after he and his two comrades decided to help the robbery victim and his wife.

Anderson's colleague, Parker, a tall, athletic youth who says he is a "sometimes student" at Franklin Adult Center, said he told his parents about the incident the next day.

"My mother said, 'That's nice.' My father said, 'That's the first time you've done something right in a while,'" Parker said, grinning broadly.

Both youths said they grew up in tough Southeast neighborhoods where crime was a way of life. Growing up on Wheeler Road, Anderson admitted he was a favorite target of local thugs.

"I got robbed. They took my minibike after knocking me off that. I got conned out of my bicycle," he said, frowning. "I'll never forget. By helping others, I guess I'm taking revenge on the people who used to do this to me."

In 1979, the D.C. police department presented 29 citizenship awards -- letters of appreciation, certificates or savings bonds valued up to $100 -- to various area residents for acts of bravery in the city. Last year 35 citizens were honored. Countless other anonymous do-gooders went unrewarded, police investigators said.