NEW YORK -- Five years ago, when he began dealing crack cocaine, he said, he and two partners made $10,000 a day. Customers came in droves to a street corner in Harlem, some buying dozens of $2, $10 and $20 vials of crack at a time.

But these days he ventures out only a few times a week, and then only in the evening. On a typical night, his crew grosses $3,000 to $4,000.

"The customers fell off, and the money fell off," said the articulate and well-groomed man in his 30s, who obviously would rather not be identified. "Business is okay. I'm making a profit. But it ain't what it used to be."

Today in upper Manhattan, in a 100-block area north of Central Park that houses some of the city's poorest residents, crack dealers still ply their trade on selected corners. Walking along Edgecombe Avenue on the edge of Washington Heights, with its twin rows of boarded-up and bombed-out brownstones, means stepping over scores of used plastic crack vials and the red, blue and yellow stoppers for them.

But the crack trade, which raged through the nation's inner cities in the 1980s and became synonymous with urban despair, is not the monster it used to be.

According to crack dealers, former crack addicts and experts in illegal drug use, the epidemic here is on the wane, victim of its extraordinary destructiveness. The generation that took to the drug five and 10 years ago is sorely depleted -- in jail, physically and emotionally exhausted by the drug or dead from the violence that accompanied it.

In a pattern that experts said is being repeated nationwide, teenagers coming of age in New York's most drug-ridden neighborhoods have seen the damage crack has done and apparently are turning against it.

"It's only people 25 and up using this drug," said Vivian Moates, 30, a mother of two who until late last year was living on the streets of Manhattan and the Bronx. She was strung out on crack, a highly addictive form of purified cocaine usually dispensed in pebble-like pellets.

"The teenagers have seen what happened to their parents and their friends," she said. "My sons have had the same experience with me. They were hurt by this. They were hurt to the point where my oldest boy even hates cigarette smoke."

In city schoolyards, teachers said children have turned the word "crack" into the worst kind of insult.

"On our playground, one of the biggest taunts I hear is 'Your mother on crack,' " said Sara Mosle, who teaches at P.S. 128, an elementary school in Washington Heights.

The slowing of the crack epidemic does not mean that drug use in general is dying in the ghettos of New York and other cities. Law enforcement officials and drug treatment counselors here say there is a modest resurgence in heroin use, particularly heroin sniffing. Others say teenagers and adults have turned from destructive use of a single drug to occasional dabbling in a variety of substances -- smoking "blunts," or cigars stuffed with marijuana and a sprinkling of cocaine, and increased alcohol use.

What the decline in crack use does show, according to experts in the drug culture, is how patterns of drug use are basically cyclical. And, they add, it demonstrates, how the most important factors in moderating drug use are not law enforcement or public campaigns so much as personal experiences of those most closely affected by the epidemic.

"The drug user is no different from anybody else," said Philippe Bourgois, an anthropologist at San Francisco State University who until recently lived in East Harlem and studied its drug culture.

"A new fad will come out and they will try it, and if it works they'll keep on doing it," Bourgois said. "Crack didn't work. They got nervous breakdowns. They lost their jobs, lost their friends. Their 15-year-old brothers and sisters watched them and said, 'I'm not going to do that.' It's the same thing that happened with heroin in the late '70s. No self-respecting teen would touch it because too many of his fathers or brothers had become burned-out junkies."

Exactly how much the crack epidemic is ebbing in New York City is difficult to assess, experts say, because there is no single, reliable indicator of illegal drug use. Virtually every possible index of crack and cocaine use over the past five years, however, shows a decline.

The number of men and women arrested here who tested positive for cocaine has dropped steadily since 1988. The number of cocaine-related arrests, almost all of which involve crack, dropped from almost 54,000 in 1989 to 37,769 in 1991, the latest year for which statistics are available. The number of births to women using cocaine and crack during pregnancy also fell, from 3,168 in 1989 to 2,239 in 1991.

In a recent report, the New York State Division of Substance Abuse Services said that "the six- or seven-person crews, which had been common in medium and heavy drug-copping locations, have largely disappeared." City narcotics officers said open-air drug markets so common in the late 1980s are drying up.

"If crack is not in decline, it's certainly leveled off," said Capt. John Fahy of the New York Police Department's narcotic division.

Much of the best direct evidence for waning crack use, however, comes from "ethnographers," anthropologists and sociologists who enter inner-city communities and establish long-term relationships with drugs users and sellers. One such group is the National Development and Research Institutes Inc. (NDRI), a Manhattan organization that has been studying crack use in Harlem and Washington Heights for several years under contract from the National Institute of Drug Addiction. The NDRI estimate, based on tracking a group of dealers in upper Manhattan, is that crack use probably peaked here in the mid-1980s and has sharply contracted in recent years.

That means the crack "cycle" here probably lasted about 10 years -- substantially shorter than the preceding epidemic involving injectable heroin, which began in the 1960s, peaked in the early 1970s and still lingers in certain neighborhoods.

The change, drug experts said, has much to do with the strikingly different pharmacological and social profiles of the two drugs. For many users, heroin was a sustainable addiction that could be maintained for many years. Crack, in contrast, produces a much more powerful and crippling high, and serving its voracious addiction is far less compatible with maintaining a normal lifestyle.

Jack Casalan, 41, a former heroin addict living in the Bronx, said he used heroin for 29 years before he became so destitute and physically spent that he sought drug treatment. That sort of history is virtually impossible with crack users.

"I saw people with college educations and jobs start crack, and in six months or a year they'd hit the same place it took me 29 years to hit," Casalan said.

Philip Garcia, 35, a recovering addict living in the Williamsburg area of Brooklyn, said he used heroin for years and switched last year to smoking crack.

"I lasted for nine months before I was at the point where I was losing control," he said.

Today, bustling open-air drug markets that flourished in central Harlem in the 1980s are almost gone, no longer profitable in a community exhausted by the excesses of the past decade.

"There used to be 100 to 200 people on the corner of 116th Street and Eighth Avenue," said Ansley Hamid, an anthropologist at the John Jay College of Criminal Justice in Manhattan who has studied drug use in New York for nearly 20 years.

"It's not that way anymore . . . . With smokable cocaine, after five years, you've lost your job, your savings. Your family doesn't want to know you. The epidemic can't go on any more than 10 years."

One dealer who is being tracked by NDRI and runs a large street-selling operation said in an interview that in the past few years, he has had to lay off six of the 18 people who once worked for him.

"As long as I have been in the street, I have known everything comes to an end," he said. " . . . I used to have to open up spots. Now I'm closing them down. The kids just aren't getting involved any more. I see a lot of kids running away from it."

He said he is thinking of switching to heroin.