HUNTING for heroin addicts in the stairwell of an unlit, urine-scented housing project, Officers Michael C. O'Hara and Richard L. Whalen pulled out their flashlights and walked upstairs. They checked out the shadows and joked grimly with each other. "How'd you like coming home to this every night?" "Sure smells nice."

Just a routine police chore in the heart of Roxbury. But, as the cops in front of us knew too well, little in the big-city policeman's life is routine.

"You need to sign these releases, in case you get killed--we lost two reporters already," Lt. Robert Faherty had cracked earlier in the evening, and we had sniggered along. Now it didn't seem so funny.

It all started innocently enough. Our escorts were right out of central casting. Boston cops O'Hara, 27, and Whalen, 26: good-humored, clean-cut, baby-faced Irishmen who had grown up in the neighborhood. Once high school rivals, they had become friends in the Academy and had been partners for 18 months.

They were the kind of cops you'd like to think were patrolling your neighborhood.

At Doughboy Donuts, our first stop, we met some of the supporting cast: wisecracking Patrolman James Carnell and his partner. James Browning. Carnell was known as the man whose Dr. Ruth Westheimer impersonations had sent a senior officer to the hospital with chest pains.

They seemed more like a comedy troupe than a police squad. Ten minutes after we'd scarfed down our dinner, however, reality struck...literally. Carnell and his partner had been broadsided in an intesection and rescue workers were cutting them out of their cruiser. They were later treated at a local hospital and released late in the evening, too late to get back on to the five-midnight shift.

Then we were flying at 75 m.p.h., screeching around corners and dodging late rush-hour traffic to get to a reported car theft.

Here we were, two scared, wimpy Harvard students, thrust into the the real world at its worst. Roxbury: the toughest precinct in the state, a place where shootings, stabbings, thievery, fights and druggies are all too commonplace.

"It's the jungle, survival of the fittest," Whalen told us. "They'll kill you. They don't cay-eh," O'Hara added.

Our initial rush proved unnecessary, as the suspicious auto theft proved to be a sidewalk car wash, not a strip--down. In the next hour, though, we found two stripped automobiles and had them towed. Some had been stolen that same day, but we didn't catch anyone.

The highlight of the early evening was driving through dog crap, an event which not only haunted us nasally for some time afterwards, but elicited the first good story.

The evening before, investigating a possible break-in, O'Hara was crawling on a rooftop when he looked down and noticed that he had rolled in something very much like cat shit, making the rest of the night shift seem days long. He was wearing his galoshes now, waiting for his dress shoes to come back from the cleaner's.

"Just my fahkin' luck," he growled, rolling up his window and turning on the air conditioner.

AROUND 7:30 p.m., our mounting blood lust was first satisfied, by word of a two-vehicle collision on Dorchester St. We had been looking forward morbidly to the gory spectacle of a good accident, but when we pulled up and saw the mangled motorcycle lying on the sidewalk, our enthusiasm turned to nausea. It had broadsided a Wagoneer.

We pushed through the growing crowd. The bike's speedometer was stuck somewhere over 50. Following Whalen, we entered the ring of spectators and saw the cyclist sprawled on the road, still in his helmet, surrounded by broken glass and paramedics. O'Hara was already questioning witnesses.

Just as the victim was being put into the ambulance, a young man claiming to be the owner of the bike appeared, fuming. Looking at his cycle, he began snarling obscenities at the victim, who had apparently borrowed it.

"Is he dead? I hope he's fucking dead," he growled, kicking the useless machine. "Who's gonna two this?"

Then there arrived the victim's mother. Still in curlers and carrying a forgotten hot fudge sundae, she approached the two officers, wailing. "Please tell me it ain't him, please tell me it ain't him," again and again at the top of her lungs. Gently putting her sundae on the trunk of the cruiser, O'Hara led her away, quietly trying to console her.

The 20-year-old victim was rushed to a nearby hospital, where he was reported in stable condition early yesterday.

For O'Hara and Whalen, the incident apparently dredged up memories of the assignment both cops agree was one of the toughest.

"We had to tell a woman that her daughter had died," Whalen recalled. "Michael couldn't find the words. That was a tough one. You want to get emotional, but you're not getting paid to be emotional. You can't take your work home with you."

But sometimes, work can hit close to home. O'Hara was particularly disturbed by the case he handled three weeks ago of a 72-year-old man who had allegedly sexually molested a 7-year-old girl. O'Hara has a five-year old daughter.

I was trying to talk to this girl and saving to myself, would I talk to my daughter like, this?" O'Hara said. "The guy said. I We want to has sex with you. I'll give you money. This was a 7-year-old kid. Then you arrest the gay and you gotta treat like a gentleman. Sometimes it appalls you but life goes on."

Atimes, life for the two officers has been appalling. Like the old woman, felled by a heart attack, who had been partially eaten by her cats before her neighbors noticed the smell. Like the man who had tied a shotgun to his head, stuck the barrel in his mouth, and pulled the trigger.

They had done a lot, too. Whalen said that while trying to get a badly stabbed man into an ambulance, he had accidentally stuck his hand into the victim's intestines. Walking through the dark with nothing but flashlights and instinct, the two cops had stalked a suspect who was toting a submachine gun.

Perhaps the best defense these man have is their sense of humor. O'Hara, for instance, followed the story of two children accidentally shot outside a bar with a riotous description of a 300-pound halter-topped nymphomaniac who frequents the spot. All of the officers seemed ready for a joke.

There is no small amount of absurdity in a policeman's life. At 10:39 p.m., we got a call in the Savin Hill area of Dorchester. A woman had reported hearing a burglar inside her building, and as we pulled up in front of the dilapidated three-story apartment house, flashing the spotlight against its facade, our stomachs knotted in tension.

As we approached, the curtains parted in the first-story window, and an old woman who looked like Ichabod Crane warbled, "He's in here! He's in here!"

Our pulses quickened when Whalen, hand on his gun, rushed into the blackness of the main hallway. Nothing happened.

O'Hara was still outside. A window had opened on the second floor, and a man bearing a strong resemblance to Uriah Heep was leaning out. O'Hara shone his light up at him. "Hey you! Is this lady nahmal down hee-an?"

"She'sh not much of a conversnationalisht, but she doeshn't give me no trouble," the strange old man yelled back, showing that if anything, he was no one to judge.

"He's downstairs!" the lady shriked appearing again in her window. There was a lot of crashing around inside, and Whalen's flishlight beam shone out through the basement windows. One of them was broken. Someone had gotten, in, and appeared to have also gotten cat.

"Who else lives hee-ah?" O'Hara shouted upstairs as he entered the building and started up the stairs. Uriah was waiting for us on the second floor in wild-eyed confusion. "He'sh an epileptic," he whinnied, pointing up at the third floor. "Take it eashy on him."

The officers banged on the third-floor door and its mysterious occupant burst out on the landing. None of us, seasoned officers included, was prepared for the sight of a pale, fish-colored man in camouflaged bikini underwear, crying. "Has there been a shooting?"

We beat a hasty retreat, postponing the investigation until the basement tenants came home and reported the break-in.

"Fahkin nahts up they-ah," hissed O'Hara.

We stopped momentarily on the street to watch an undercover drug bust which had occurred on the corner during our tour of the funhouse. We left as one of the narcs was shaking down a pimply young suspect.

And so it went, for seven hours on the beat.

WHALEN and O'Hara are good, hardworking cops, and largely unappreciated. We felt the same hostile sidewalk stares that they did. We saw few people thank them. We watched them grab a man who had his hands around the throat of a young woman in a barroom doorway. The woman called them pigs.

The officers said they are frustrated sometimes that manpower is short and some suspects get away on plea bargains or technicalities. Sometimes the cops wonder what they're doing out there.

"Sometimes it's futile," said O'Hara, "but you have to do it. Otherwise everybody would be doing anything they want out they-ah. And to the guy on the street who goes to work, it means we'll come if he calls. You have to have something, right? It's bettah than nuthin."