SITTING ON the balcony above their sparkling new deli on Third Avenue and 43rd Street, Doug and Haesu Choi face an uncertain future. Like many Korean Americans who have come to this country, their experiences have included an unsettling mix of marginal triumphs and near failures.

First they were forced to sell a produce stand they had borrowed thousands of dollars to open after a fellow immigrant started a competing business next door, igniting a brutal price war. Then the Chois opened a stationery store, but the business suffered from a dismal economy and the lack of a stable client base. So they borrowed $65,000 from three communal savings pools known as gaes and opened yet another deli. That was more than a year ago, and they are barely breaking even.

"We have to succeed because of all the people who put their trust in us and tried to help," explains Haesu, a statuesque woman whose short straight hair frames an angular jaw.

It is well-known by now that Korean Americans' unflagging enterprise has powerfully boosted the economy of urban areas around the country. In New York alone, Koreans own 85 percent of produce stands, 70 percent of grocery stores, 80 percent of nail salons and 60 percent of dry cleaners. Their strong family ties and indefatigable work ethic have given these immigrants the highest rate of entrepreneurship in the country: 28 percent of Korean American men and 20 percent of women own their own business, according to the National Bureau of Economic Research.

But of late, Korean Americans have experienced some economic and cultural jolts that make clear just how big the task of building the urban future will be. While early arrivals have prospered, recent immigrants are facing far more precarious circumstances. Battered by punishing taxes and regulations, by brutalizing crime and by stiff competition within their own community, more and more Korean businesses are failing, leaving their owners questioning whether America offers the opportunity they had envisioned. Between 1991 and 1994, Korean leaders estimate that at least 1,600 Korean-owned stores went bankrupt in New York alone.

"Koreans don't announce their bankruptcy, because they feel shame and want to disappear," says Bong Jin Sa, executive director of the Korean Produce Association. "But we see the doors closed."

Dispirited by all the problems they face, between 4 and 5 percent of New York's Korean population, or about a thousand families a year, are returning to Korea, where word of Korean Americans' long hours and decreasing returns has begun to spread. Those who return are in for a surprise: Koreans who stayed home are doing better than those who left, thanks to Korea's booming economy. As a result, immigration has slowed to a trickle: The New York City Planning Department estimates that only 1,500 Koreans have been entering the city annually in the '90s.

To varying degrees, the recent experiences of Korean Americans in New York are being played out in major cities nationwide. In Los Angeles and Washington, two other prime entry points for Koreans in this country, the struggles against racial tensions and violent crime are much the same. In Baltimore, already tense relations between Koreans and blacks have recently escalated over city renovation plans that could push many Korean business owners out of their locations.

If policy makers are serious about rejuvenating this country's blighted inner cities, they should be paying close attention. It is Koreans, after all, who today offer the most vivid proof that the American Dream is still alive. They have gone into urban areas most retailers have shunned, turning service into an art form and teaching traditional business something about sheer will and fortitude. That their dream is in trouble suggests how difficult it will be to bring jobs and growth to the most troubled urban areas. The story of Byong Lim, who took over the Chois' troubled stationery business on the Upper East Side, is typical of the troubles many Korean Americans are facing. Lim and his American wife would like to close the store on Sundays, but they can't afford to forego the $250 to $300 the day brings in. He pays $4,500 in rent and $500 in taxes each month; the city's 8.25 percent sales tax drives many would-be customers to illegal street vendors. "I feel really trapped," he says.

Because of their willingness to open businesses in neglected inner-city areas, problems with shoplifting and even armed burglaries have become an accepted, if harrowing, part of many Korean retailers' experience. Ok Sun Kim and her husband worked 70-hour weeks for eight years to save enough money to set up their own business. Yet after they opened their grocery store in Brooklyn four years ago, their dream quickly soured. In just six months, they endured a boycott by black residents in the neighborhood, an attempted robbery and a bludgeoning in another attack. Then their store was burned to the ground in what they charge was a bias crime.

Though the most violent cases make the news, much of the crime against Korean merchants goes unnoticed because the Koreans don't report it.

According to Bong Jin Sa of the Korean Produce Association, Koreans feel ashamed if they are attacked and so they are reluctant to tell the authorities. When they do report crimes, they rarely get satisfaction, Sa says, so they have stopped bothering. The produce association has launched a campaign to persuade shop owners to report all crimes and not to resist or chase criminals, who may be armed. However dangerous it is, shop owners feel they must fight back against criminals. Doug Choi says he experiences constant shoplifting, and has learned to go after the criminals himself. "People ask, Why go after someone for 60 cents?' But if I let him go, he comes again. By the time I'm leaving him alone, my store is empty."

Choi has paid a price for his vigilance. In late 1994 someone filled up a tray from the salad bar and walked out of the store. Choi chased after him and asked the man what he was doing. The shoplifter knocked Choi unconscious. Choi's face was swollen for two weeks, and he still has a scar.

The crime that besets Korean entrepreneurs is in some cases aggravated by racial tensions that seem only to be intensifying. Many blacks see Korean merchants the way some saw their Jewish predecessors: as opportunists trying to get rich off the poor.

"Koreans are the most successful business group in the black community, which is why they target us," says Kee Young Lee of the Korean News.

In recent years, these tensions have led to demands that Koreans provide employment and financial support to the communities where their businesses thrive. Those Koreans who don't comply may face boycotts or even violence.

In 1990, a nine-month racial boycott drove two Korean produce stores in Flatbush, Brooklyn, out of business. Black activists, led by the Rev. Al Sharpton, the city's best-known racial provocateur, charged that employees of the Red Apple market had beaten up a Haitian woman for no reason; the manager denied the accusation. The administration of then-Mayor David Dinkins refused to enforce a court order banning protests within 50 feet of Red Apple and a neighboring store that had been drawn into the dispute.

But nothing has had as profound an impact on Koreans' ideas about America as the 1992 Los Angeles riots. Six hundred Korean American businesses in South Central Los Angeles and 200 in Koreatown were damaged or destroyed; Koreans sustained 45 percent of all riot damage. In the South Bronx, an armed gang vandalized a Korean dry cleaner in sympathy with the Los Angeles rioters, and vandals shattered the windows of a Korean grocer in Bedford-Stuyvesant as they taunted him with a racist rap song. Though deeply shaken, the Korean business community has turned the other cheek in an effort to ease escalating racial tensions. In February 1993, the same Al Sharpton who led the Flatbush boycott gave the invocation at the annual awards dinner of the Korean American Grocers Association of New York. For four years Korean grocers have distributed "love turkeys" at Thanksgiving through 3,000 churches in minority neighborhoods; they also sponsor spots on black radio stations honoring black heroes.

No other group of small-business owners is subject to such pressure to redistribute its resources, and no other has responded with such a variety of initiatives. Yet these efforts provide no more certain a guarantee against racial animosity than did similar efforts in Los Angeles before the riots. When Mayor Rudolph Giuliani ousted more than 1,000 illegal street vendors on 125th Street in Harlem in October 1994, a local Nation of Islam mosque organized a short-lived "Buy Black" boycott of non-black merchants on the street.

Won Duck Kim, owner of the Guy and Gal clothing store, was one of the targets of that boycott. Kim is hardly insensitive to black concerns: He proudly displays pictures of himself with former Mayor Dinkins, Rep. Charles Rangel and other black leaders. Awards from black organizations line the top of one 40-foot wall. Malcolm X and Martin Luther King posters cover his cashier stand. He supports the Harlem Boys Choir. In 1990 he helped organize a nine-day trip to Korea by 37 black preachers. Asked his opinion of the demand to give back to the community, Kim merely says that "new immigrants can't jump over buildings."

Tony, one of his two black employees, is more outspoken: "My boss is supporting the community by being here. He has done more than his share -- he gives 300 percent. Even in Buy Black' stores, the owners don't support the community."

Spurred by racial tensions and commercial concerns, Korean Americans are gradually beginning to flex their political muscle. "Flatbush was the first time we realized we needed political power," says Chun Soo Pyun of the Korean Community Services of Metropolitan New York. When Pyun organized a City Hall rally to demand that Mayor Dinkins enforce the court order against picketing, between 7,000 and 10,000 protesters showed up; voter registration was brisk.

Political activism doesn't come naturally to Koreans, whose culture does not emphasize democratic participation, and who have little expectation that government institutions can help them. Many Koreans are afraid to fill out census forms or register to vote. If they do register, their grueling hours make it hard to get to the polls. Little wonder the two major centers of Korean American population, the cities of New York and Los Angeles, have no Koreans in public office.

Slowly, that is starting to change. In 1992 Diamond Bar, Calif., sent the first Korean American Republican, Jay Kim, to Congress. Across the country 11 Korean Americans, nearly all Republicans, hold government office. In Baltimore, Korean business owners have recently formed a political action committee to raise money for local election campaigns this year.

How many Korean Americans will give up on their dream of making it in America? Though there is early evidence that thousands already have, certainly many remain determined to see their aspirations through. Doug and Haesu Choi know now that hard work and discipline alone will not guarantee permanent success, but they remain committed to making a go of it in New York.

Asked why they don't move their business out of New York closer to their New Jersey home, Haesu exclaims: "I love this city. In the whole world, you can't find another like it." But she rues its decline: "It's changed so much since 1975. It's really a shame. People used to pay more attention to each other and their surroundings." Can the Koreans contribute to the city's revival? "The Koreans are still a small percentage compared to other immigrants," Haesu says. "But we hope that as the second generation grows up, they will do something to make it better." Heather MacDonald is a contributing editor of the Manhattan Institute's City Journal, from which this article is adapted.