The white populations of the District, Arlington and Alexandria have grown this decade even as the region's outer counties have grown more diverse, according to new census estimates to be released today that underscore how the area's soaring housing prices and job sprawl are reshaping its racial and ethnic dynamics.

The city and those close-in Virginia suburbs had higher percentages of non-Hispanic white residents in 2004 than in 2000, a reversal of past trends, the estimates say. Minority groups grew more slowly than in the past, or declined.

In the District, Arlington and Alexandria, whites became a larger share of the population -- by a rate that ranked in the top 10 among the nation's jurisdictions, according to Brookings Institution demographer William H. Frey. Whites account for 30 percent of the D.C. population, up from 28 percent in 2000, and their numbers rose 3 percentage points in both Arlington, to 64 percent, and Alexandria, to 58 percent.

Unlike closer-in communities, counties outside the Capital Beltway experienced faster growth among minorities during those same years. The number of whites, blacks, Asians and Hispanics generally rose, according to the new estimates, but numbers of nonwhites rose more sharply. By Frey's calculations, the rate of minority growth in five jurisdictions -- Manassas Park, Prince William County, Loudoun County, Charles County and Manassas -- ranked in the top dozen nationally.

Overall, according to Census Bureau estimates, the Washington area's 5.9 million people are 56 percent non-Hispanic white, 25 percent black, 8 percent Asian and 10 percent Hispanic. All groups grew in number, but Asians and Hispanics continued to increase most rapidly.

Frey said the diversification of the region's outer counties meshes with what's happening nationally on the fringe of urban areas. But the growing white population in the District and two close-in counties stands out among metropolitan areas, he said, reflecting the desirability of core neighborhoods among those who can afford to move there, who are most likely to be white.

"It's a hot housing market where there's a single defined center," he said. "There are other hot housing markets in other parts of the country -- San Diego, Los Angeles -- but D.C. has a single and important center where a lot of these young professionals want to be."

The region's racial and ethnic changes reflect a range of social forces. The District is again a desirable place to live, and some African Americans are concerned about being pushed out. Arlington and Alexandria offer "a lighter form of urbanity," in the words of Virginia Tech demographer Robert E. Lang, for people weary of gridlock who can afford to pay $1 million for a townhouse.

But real estate fever has crimped the supply of affordable housing, squeezing out minorities, who generally are less affluent. Immigration to Arlington and Alexandria has slowed, with new arrivals moving to where most new jobs are, in less expensive communities beyond the Beltway.

One neighborhood being transformed by new arrivals and rising prices is Del Ray, a stylish quarter of quirky bungalows, artsy shops and walk-to restaurants in Alexandria, a city where residential real estate assessments rose 77 percent in the past three years. The Altenburgs -- Larry, 34, and Debbie, 31 -- made 10 unsuccessful bids before they bought a two-story yellow 1920s house there last year. They moved from Fairfax County because they were attracted to Del Ray's small-town feel as well as its diversity.

Larry Altenburg, a consultant for Booz Allen Hamilton who is treasurer of the Del Ray Citizens Association, said the neighborhood's complexion and economics have changed noticeably, thanks in part to eager newcomers who in some cases bought houses from longtime African American residents. Civic association meetings, he said, are filled with mostly white faces.

"It's hard not to notice," Altenburg said. "You can see that the growth of the core of the area of Del Ray has become much more white and less African American, but there's still a great feeling of diversity."

In the District, Urban Institute researchers studying home mortgage data have found a pattern similar to that shown by the new census estimates. "The share of minorities among home buyers is dropping, especially among some of the most diverse neighborhoods experiencing the most price pressures," said researcher Margery Austin Turner. "Many minority families may be getting priced out of the District market at the same time the District is getting more attractive to a wider variety of families."

Still, she said, this growing affluence "potentially brings vitality and resources that the city can take advantage of to address the affordability and diversity problems."

The District's black majority, now 57 percent, has been declining for years, and some longtime African American residents worry that their concerns will be frozen out by an increasingly powerful white electorate. But civil rights activist Lawrence T. Guyot Jr. said those worries can be addressed.

"If we are honest about having an open dialogue on race before it's too late, we can deal with anything," said Guyot, who lives in the gentrifying LeDroit Park neighborhood near Howard University.

"We as a city had better be concerned about maintaining as many black people as we can, simply because they've earned the right to be here. They were here when there was nothing here to fight for," Guyot said. But, he said, "the converse of that is not true. We should be smart enough and creative enough to do that without saying no one else is welcome."

Larry and Debbie Altenburg moved from Fairfax County to Alexandria, where home prices have risen sharply and the minority population has dropped.