After shedding residents for decades, many U.S. cities revived in the 1990s, with immigrants streaming in and gentrification resurrecting downtowns with lofts, coffee bars and trendy restaurants.

But new Census Bureau estimates to be released today show many cities slipping again. More than two dozen large cities that had been growing a decade ago are shrinking. Fast-growing suburbs with service-sector jobs and more affordable housing are attracting thousands of foreign-born residents who in the past would have started out in the city.

The list of former gainers that have lost population since 2000 include Boston, Chicago, Minneapolis and San Francisco.

"The broad swing of things is that people move out. For a lot of people, the city is simply a way station, and it's not clear how long these rosy times of the late '90s would continue," said William H. Frey, a Brookings Institution demographer. "We're clearly going in a somewhat different direction than we were in the late '90s."

Among the nation's 251 cities with at least 100,000 people, 68 lost population between 2000 and 2004, according to the new figures. In the 1990s, 36 did.

Regionally, the biggest change was in the Midwest, where a third of cities lost population in the 1990s but more than 60 percent did this decade, according to Frey's calculations. The South and West also have more losing cities this decade, including San Francisco and nearby Oakland, where demographers blamed high housing prices and the collapse of the high-tech economy. Frey's analysis also found that expansion slowed in some formerly fast-growing cities.

The only region that has fewer shrinking cities this decade is the Northeast, where some older places such as Newark, N.J., and New Haven, Conn., have rebounded after decades of loss. The estimates found that New York City has kept growing since 2000, and that longtime population-losing older cities such as Cleveland and Philadelphia continued to shrink.

Census Bureau figures released earlier said the District and Baltimore have continued to lose population, as they have every decade since the 1950s. City officials in Washington and Baltimore -- as in Boston, Chicago and some other cities -- dispute the figures, saying they undercount immigrants and new housing units. Census Bureau demographer Greg Harper said the agency has improved its count of both since the 1990s.

But urban experts say they are convinced that the general trend of city population loss this decade is real. In retrospect, the gains that made the 1990s the best decade for big cities since World War II may have been a temporary exception to the long-term pattern. Except for those who can afford high-priced city housing, the lure of the suburbs is too strong, they say.

In Chicago -- "the toast of the '90s metro revival," in Frey's words -- the population dropped by nearly 34,000 this decade, the largest loss among former gainers. The city grew in the 1990s for the first time in half a century, mainly because thousands of Hispanic immigrants and births offset departures of other residents to the suburbs.

Kenneth Johnson, a demographer at Loyola University Chicago, said Hispanic families have begun leaving the city in larger numbers for suburban safety and better schools, while some young, single immigrants head directly for outer suburbs that have a growing pool of jobs in construction, cleaning and other fields.

"What's probably happening is there's still a reasonably large influx of unattached Hispanics into the city -- though not the volume as in the '90s," he said. "But I think the city is losing Hispanic families for the same reasons it is losing white families and black families," he said.

The main Hispanic neighborhoods in the heart of Chicago, including Pilsen, Little Village and Back of the Yards, have almost no green space. Luis Gutierrez, executive director of the organization Latinos Progresando in the Pilsen neighborhood, said once a family moves to the suburbs, it starts a chain reaction by which relatives and friends arriving from Mexico join them there, bypassing the city.

"My sister moved out to Elgin to be closer to her job," he said. "Then, when her mother-in-law and brother-in-law came, they stayed in Elgin out there with her, not in Chicago. Because of that, places like Elgin are doubling in size."

In Boston, economist Paul Harrington of Northeastern University's Center for Labor Market Studies said the city was hurt by the collapse of the high-tech economy that also damaged San Francisco and other highflying urban centers of the 1990s. Boston's job base shrank 7 percent from late 2001 to late 2004, he said.

"The job creation in the city and state has just been poor," he said. "To see this slowdown and population decline is not surprising in the context of that job performance."

But demographers emphasize that population growth is not the only measure of a city's success. In Washington, which has been losing population for years, "its housing market is stronger and its fiscal markets are stronger than it was 100,000 people ago," said Robert Lang, director of the Metropolitan Center at Virginia Tech.

Like other cities whose reputations but not populaces are growing, he said, "if you promote yourself to singles, childless couples, gays, the creative class, that's not going to grow your population, but it's going to grow your municipal budget."

Staff writer Kari Lydersen in Chicago contributed to this report.

The San Francisco area suffered after the high-tech economy's collapse.Chicago's population losses are attributed to movement to the suburbs.Boston's job base shrank 7 percent from late 2001 to late 2004.