A quarter of a century has passed since Michael Lomax, a leader of modern Atlanta and symbol of its rising black middle class, made his first trip to the South. His mother drove. He and his five brothers and sisters jostled for space on the long-distance haul from the West Coast. The place names of their overnight stops still stick in his mind. Amarillo, Texas. Shreveport, Louisiana. Mobile, Alabama. He even remembers the motels. In Amarillo it was Las Luces.

The route was not direct, but it was the only route for the Lomax family in 1961. There were few motels where blacks could stay.

Three years later Lomax came to Atlanta to go to college. On the day he arrived to begin his education at Morehouse, one of the finest black colleges in the country, Lomax got lost. His mother pulled the car over to a curb near the state capitol; the sidewalks were lined with white people. They asked one stranger after another for directions to Morehouse.

No, said the white Atlantans. Morehouse? No. No idea.

It was less than a mile away.

During Lomax's years at Morehouse, the trolleys and lunch counters of Atlanta became integrated, and blacks for the first time worked alongside whites on the police and firefighting forces. The city's business establishment began an alliance with black leaders that helped the city avoid the riots of Detroit and Watts. But physical barriers were also built in what blacks viewed as an attempt to assure the segregation of some neighborhoods. The most notorious was a new street devised by the administration of Mayor Ivan Allen, usually viewed as progressive in racial and other matters. This fenced-in right of way created numerous dead-ends on streets running north-south. Blacks called it the Berlin Wall.

Downtown was still a frightening place for a young black scholar. "Would you go to City Hall? No. Never," Lomax said. "Would you be treated ill if you did? Yes."

Lomax was graduated in the spring of 1968, the spring that the Rev. Martin Luther King Jr., another Morehouse man, was assassinated. Now, at age 38, he is a person of letters and of political influence. He is an associate professor of literature at Spelman College, the black women's school adjoining Morehouse, a lecturer at the University of Georgia, the big state school that was all-white when his higher education began, and he is the first black chairman of the Board of Commissioners in Fulton County, which includes most of Atlanta and its near suburbs. He is among those at the forefront of Atlanta's young black middle class, a group that in many ways defines the southern hub's politics and culture and is beginning to define its economics as well.

After demanding equality and learning how to negotiate in two worlds -- one white, one black -- these successful blacks are confronted today with another version of the two-worlds proposition: one black and the other black, the rising middle class and the chronically poor who have come to be known as the underclass. They wonder whether there is a Berlin Wall dividing their own people.

"For generations the belief was that legal reform would transform the black community -- and that came in the 1960s," Lomax said. "After the civil rights laws were enacted, the belief was that we needed the political power to enforce and shape them. In the 1970s we started getting that power. Then with the 1980 census came the gut-kicker. We found that for all the laws and political gains, there still existed a substantial underclass. One-quarter of the black families in Fulton County are at or below the poverty line. That's multigenerational. You can't go out and rail against it, you can't go out and pass laws to change it."

"There are two black Atlantas, no doubt about it," said Labat Yancey, Lomax's classmate at Morehouse, now an executive with an information-processing firm. "Middle-class blacks move around the city; they know each other, they network. Other segments of the population are out there catching hell from day to day."

What is the obligation of middle-class blacks to those "catching hell?" Do successful blacks feel that they are doing as much as they should? What role do race and class play in their daily lives? That is the focus of this report, based in large part on interviews with people who were graduated from the city's black colleges in 1968, stayed in Atlanta, prospered with their changing city and now, as they approach 40, are at the prime of their lives. Success Brings Message of Burdens

If life is going well for many of these young blacks, they exude anxiety about the fragility of their status. That was most evident in conversations about the obligations they say they feel to help the poor -- obligations they are not certain they are fulfilling. Questions about their relationship with the underclass can evoke anger. Many of them feel black first, middle-class second; black forever, financially secure for the time being. They feel caught in a paradox that Anna Grant, dean of the sociology department at Morehouse, expressed:

"The message America is sending us is: Whatever you do, you haven't arrived yet because you haven't brought the rest of your race up with you. You've got to go back and save all the rest before we'll admit you. Well, there's no way to redeem all the black people in our society. We aren't all saints, and we aren't all sinners. Those who succeed find themselves damned if we do and damned if we don't."

Lomax, who as chairman of the Fulton County commission oversees programs for criminal justice and health care, held a similar view.

"It's very easy for white people to say that the black middle class is abandoning the underclass," he said. "It's very simplistic. The reason is whites are uncomfortable being with aggressive, determined blacks who play by the same rules. . . . It's insulting! Just because I know how to tie my tie, how to use a fork, because I might be fluent in French, that merely means I'm acculturated, it doesn't mean, 'Isn't he a good-looking white guy who wants to forget his race?' For generations, black parents trained their children to compete. Now this is the generation that can compete, and they're saying, 'You're not black; you're white.' "

But is it a white-imposed notion that successful blacks should feel more responsibility for the poor, as Grant and Lomax said? According to the Washington Post-ABC News nationwide poll on black attitudes, 80 percent of those surveyed said they believed that blacks who were financially well-off should be doing more to help the poor. There were no variations on that percentage north or south, rich or underclass; four of every five respondents in every group said more should be done.

"I would have to say that there is a lot of room for improvement," said Vivian Snellings Baskerville, a 1968 graduate of Clark College. "We learned at Clark that you don't have to be rich to be a blessing. What affects one of us affects us all. For a time I've felt that there wasn't enough caring among those of us who can help." Center of Education And Enterprise

Atlanta has long been considered a mecca for the black middle class. In recent years, according to a census analysis by Charles Jaret of Georgia State University, black migration has been extraordinary. The net migration of blacks to Atlanta (the number arriving minus the number leaving) was greater between 1975 and 1980 than to any other city in the United States -- a gain of 28,147 blacks from elsewhere.

For generations the city's beacon was education, specifically the Atlanta University Center, a cluster of black colleges off Hunter Street -- now known as Martin Luther King Drive -- including Morehouse, Spelman, Clark, Morris Brown, Interdenominational Theological Center and the Atlanta University graduate school. The schools are at the core of black intellectual life here; they are still, in a sense, the womb, as Lomax said, but they are no longer the only sources of black middle-class sustenance.

Atlanta's buoyant local economy and black political leadership -- headed since 1973 by Mayors Maynard Jackson and Andrew Young -- gave it a national reputation as a city where blacks can make it. Seven of the top 100 black enterprises in the United States are located here. The Atlanta Life Insurance Co. is the largest black-owned stock insurance company in the nation. The black-run Citizens Trust Company Bank provides mortgages for hundreds of black homeowners. International and regional corporations from IBM to Citizens and Southern National Bank employ dozens of blacks in management.

Veronica Biggins, class of '68 at Spelman, is a senior vice president for personnel at Citizens and Southern, the Southeast's sixth-largest financial institution. The revolutionary Afro hair style she once loved has been tamed into graying curls. Not until her sophomore year at Spelman were blacks allowed to eat at the lunch counter of Rich's department store downtown. Now she dines at the Ritz-Carlton. Like many of her classmates, she has grown comfortable in the integrated business society to which much of Atlanta's black middle class belongs. She works for white people, with white people and over white people.

She is concerned that integration has brought with it a danger for blacks that their heritage will be abandoned. "I think where we are today is black folks trying to be white, which in my mind is not integration," she said. The mission of her generation of achievers is to push more money into the black community. She said she feels she is doing her part as a personnel manager, helping blacks advance into the management levels of her bank.

Welfare, on the other hand, is "the biggest issue that has affected black people in America," she said. "As long as I can look up and know that somebody else is going to take care of me, why should I do anything?"

James Jester, a lawyer and '68 graduate of Morris Brown College, agrees with Biggins about the importance of achieving economic power. He is less certain about the negative impact of welfare.

The son of a textile worker, Jester came to Atlanta from rural Barnesville, Ga. He dropped out of school once for financial reasons. When he came back, he borrowed $1 from a friend, $1 from his parents and $1 from his brother to buy the bus ticket to the big city. He arrived at a boarding house near Morris Brown and borrowed $5 from an elderly man for food. He bought a loaf of bread, a package of bologna and a jar of mayonnaise, made a batch of sandwiches and placed them back in the bread wrapper. He was nourished for a day, but then the sandwiches started rotting; there was no refrigerator.

"There is nothing wrong with welfare for those who need the money to survive," Jester said. "There are a few blacks who insist that there is no such thing as discrimination. They say the only reason poor blacks can't make it is because of government relief. I run into blacks like that at parties around town. But not too many. The real question is not whether we are doing enough but what we should be doing. How do you help? A lot of us graduated in the late 1960s with majors in the social sciences, and with all our wisdom we can't figure it out."

In their own ways, Biggins and Jester expressed the same thesis as Lomax and Grant concerning expectations of the black middle class. As professor, bank official or attorney, they were role models and their jobs were measures of advancement for all blacks. "Are white sociology professors asked whether they do enough for the chronic poor of Appalachia?" Grant asked.

William Shepherd, a graduate of Morris Brown, is a lawyer and lecturer on constitutional law. He grew up poor in Atlanta and traveled along as his father delivered coal to the houses of rich whites. Shepherd was so sharp with numbers that by the time he was 12 he was a better accountant than his father's superiors, and on weekends they had him balance the books. Then one of the whites at the coal company opened a shoe store in Buckhead, the exclusive white neighborhood, and recruited Shepherd, age 14, to keep the records and shine shoes -- perhaps the perfect metaphor for internal conflict in the black middle class. Keep the records and shine the shoes.

The former task was easier than the latter, because women often came in to have their shoes shined and Shepherd feared that one of them would accuse him of looking up her skirt. "I got so nervous I wouldn't even look at the shoes," he said. "Sometimes I ended up getting a little polish on the stockings."

Vivian Baskerville, who lives with her husband and two children in south Decatur, about 10 miles east of Atlanta, remembers how the white minister of Green Forest Baptist Church recruited her. The neighborhood was in transition. The church was 80 percent white. Baskerville sought assurances that it would remain integrated. The minister said everyone who wanted to leave had already left.

"We joined in June and the minister was gone by October," Baskerville said. "It was we join on Sunday, you move on Monday. We pray together in the summer, you move in the fall. The whites left all at once, and they gave such fantastic reasons for leaving."

Blacks are reminded of their color when they see whites flee. As Jane Smith Browning, Spelman class of '68, said of the families of Andrew Young, Maynard Jackson and state Sen. Julian Bond: "Andy's daddy was a dentist. Maynard's was a physician. Julian's was one of the greatest historians in the history of Atlanta University. But we all know that no matter what happens, when it comes down to it, the fact is we're all still black."

Grant remembers when the president of Morehouse during the 1960s, Benjamin E. Mays, became the first black to move to the tree-shrouded area of southwest Atlanta. "Dr. Mays moved out there and the whites started flying. They started running away from perfectly respectable blacks, blacks who by and large were better educated than them." The neighborhood is about 95 percent black now. It has been home to Lomax, Mayors Young and Jackson, Grant and baseball's immortal Henry Aaron.

Many of those who live in the Cascade Heights area of southwest Atlanta, including Lomax and Yancey, send their children to private schools. Lomax, who contends that quality education is the key to lifting blacks out of poverty, said he feels no guilt or contradiction in taking his daughter, and thus his support, out of the Atlanta school system, which he considers inadequate. He wants her to have the best of both worlds, to get a fine education but never forget her heritage. Today's Students Discuss Self-Interest

At noon on the quadrangle of Atlanta University one day last week, a few dozen people linked arms to sing and pray in memory of Martin Luther King Jr. The ceremony lasted 15 minutes. Student government president Michael Q. Parker had rented a bullhorn to address a crowd he had hoped would be many times larger than it was. He turned away from the small gathering in disappointment.

"A lot of us are the product of the 'me generation,' " said Parker, 27, a business student who was 10 when he heard about King's assassination from state troopers who boarded the bus he was riding in North Carolina. "We're about getting a nice house, a nice car, maybe a family if it fits into the financial plan. But when people aren't willing to take 15 minutes out to sing three stanzas of 'We Shall Overcome,' that's a tragedy."

An hour later, on the adjoining campus of Morehouse, 20 freshmen sat in Ida Rousseau-Mukenge's sociology classroom and debated the same issue.

"There are some blacks here who are from a lower class level that act like if they look back where they came from, they might get stuck back there somehow," said William James of Columbus, Ga.

"A lot of black people who are upper middle class have the idea that they just want to better themselves instead of black people as a whole," added David Davis of Youngstown, Ohio.

They are in their fifth month at Morehouse. When their elders in the class of 1968 were here, the school was a training ground for black doctors and lawyers. Today, two-thirds of the students are majoring in business administration. Most of those in Rousseau-Mukenge's class identified their families as middle class; a few said they were upper class, a few, poor. The young men wearing closely cropped hair, a few in leather jackets, many in high-topped sneakers, held forth in an overheated classroom on a cold day, their nascent opinions on race, social responsibility and the price of success clashing at times with their consciences.

"In the 1980s everybody is more competitive," said Lee Sanders of Dayton, Ohio. "It's dog-eat-dog, and that's what everyone was telling me even before I came to college. If you want to succeed, you can't always be concerned with the other person."

Tyrone Catlin from Long Island and Kevin Whalum, a preacher's son from Memphis, disputed this. The two young men, sitting side by side, spoke of responsibility.

"If you reap all the benefits, it just seems natural that you should pass them on if you can," said Catlin, who described his family as poor.

Whalum, who said his father runs the largest black Baptist Church in Tennessee, described his family as upper class. His father, he said, pays back the community that helped him prosper by renovating old houses and renting them for $70 or $80 a month to low-income families. "What he has done has enriched that community," Whalum said. "And they don't look at him as being -- excuse my language -- one of those 'uppity niggers.' He's one of those who made it and gave it right back."

David Tootle of Columbia, Md., was born the year Martin Luther King died. He decided to study at a black college after attending predominantly white schools all his life.

"If you can't help now, fine," Tootle said. "Get your education. Get to a point where you can help. And when you get to that point, do what you can, however little it may be. You'll have a lot more respect for yourself knowing that it took me longer to get there, but eventually you can say 'I'm there and I'm giving something back to my people.' "