A dramatic transformation is underway in the Washington area as hundreds of new condominium projects move off the drawing boards and into people's lives.

More than 47,000 new condominiums, in 322 separate projects, are coming onto the market in the next three years, according to real estate information firm Delta Associates. Many of those buildings promise to create new kinds of neighborhoods in areas that were not previously known as residential communities. At the end of September, there were 18,872 new condominium units for sale in the region, many that introduce new choices to long-established places, up from only 3,083 in the same month two years earlier.

New urban-style high-rise and mid-rise condominiums are being built in Tysons Corner, Reston, Alexandria, Shirlington, Arlington, Rockville and Bethesda. New neighborhoods are being created in emerging housing nodes around the District, including the 14th Street corridor, Columbia Heights, the Chinatown area, near Pennsylvania Avenue NW downtown and the streets around the New York Avenue Metro station in Northeast Washington. Historic adaptations of vintage buildings are introducing new twists on old themes.

And on the lower end of the price scale, about 24 apartment complexes throughout the region have been purchased by developers in the past year for conversion to condominiums, many being marketed to the middle-income people who have been left out of the recent housing boom.

But while many people are applauding the burgeoning array of choices after several years in which the competition for housing left buyers feeling more like beggars, others are wondering whether too much condominium construction is underway -- and whether a glut is looming.

That could mean lower prices, a plus for buyers. But more new units can make it harder for owners of existing condos to sell. The number of existing, for-sale condos in Alexandria and Arlington, for example, has risen from as low as 41 units at various points to a recent high of 335 units for sale, said real estate agent Ginger Harden. These days, she watches with some alarm when new condos come on the market.

"Every time you turn and you see a sign 'Coming Soon,' my real concern is whether the market will get flooded," Harden said. "It can be too much of the same thing."

Others argue that in high-priced housing markets, condominiums are the only affordable option left for many buyers -- and that the market will thus remain strong. The explosion in condos in the Washington area is being mirrored in South Florida, California, Boston and New York, other places where the gap has grown between housing prices and the incomes earned by average workers.

"It's taking place in all the areas where single-family homes are becoming unaffordable for your average first-time or middle-income buyer," said Dan Fasulo, director of market analysis for Real Capital Analytics, a New York City real estate information firm. "Not that many people can afford a half-million-plus for a starter home."

Fasulo thinks demand may be weaker at the high end of the market, where fewer people can afford the units, while he has confidence that demand will remain high for condominiums that many people can actually purchase.

"Even plain-vanilla, nondescript units will be absorbed," he said. "I wonder about the luxury unit more."

So far, condo demand remains high. More than 10,100 new units have been sold in the first three quarters of 2005, more than the 9,100 sold in the region in all of 2004, according to Delta Associates.

The increase in supply is likely to bring some moderation in pricing, said Dick Bryan, president of the Vienna-based Bryan Group, a real estate marketing firm. "We can't afford to appreciate at 22 to 28 percent a year or we price ourselves right out of the market," said Bryan, who believes the infusion of new units will help restore a better supply-and-demand balance in the condo market.

Some of the new action is coming to the suburbs, as high-rise urban living is introduced into regional hubs known mostly as job centers and shopping meccas.

The first high-rise condominium in Tysons Corner in more than two decades hit the market last month. Called Park Crest, the complex is almost across the street from Tysons II shopping mall and will feature a 19-story residential tower, along with a grocery store and retail shops. Units there are priced from $500,000 to more $2 million. In the first two weeks alone, 110 of the units have been purchased, mostly by Northern Virginians, said David Mayhood, president of the Mayhood Co., which is marketing the project. Buyers are a mix of young professionals and empty-nesters, he said.

High-rise urban-style homes are coming to Reston Town Center, too. Vienna-based KSI Services Inc. is building twin 21-story towers overlooking the area's retail core, which KSI Chairman Robert C. Kettler describes as creating a new "vertical community" there. Next week, at a ceremony that will be attended by Reston's founder, 91-year-old Robert E. Simon, KSI will deed the land to a nearby 1.25-acre park to a nonprofit Reston group, providing the area with a bit of open green space and tiered seating for open-air concerts.

On the other side of the region, the city of Rockville, which made a disastrous foray into urban renewal in the 1960s when it plopped a mall in the center of its historic old downtown, is finally remaking itself. A new project, called Rockville Town Square, is under construction. It will feature condos in five buildings, each five or six stories high, in walking distance to existing restaurants and a movie theater. The new complex will also include stores, a public library and a cultural arts center.

"It's the project all the prior mayors of Rockville were unsuccessful at building," said lawyer Steven VanGrack, vice chairman of the Maryland Real Estate Commission and a former Rockville mayor. VanGrack credits Rockville's current mayor, Larry Giammo, for its progress.

The Rockville project is representative of dogged efforts by some local governments to promote denser development on major transit lines and highways and near job centers, in places such as Clarendon, Rosslyn and Silver Spring, rather than encouraging endless sprawl outward.

"The political movement is away from developing greenfields where there is no infrastructure and more toward steering development back to the urban cores," said Fasulo of Real Capital Analytics. "It's not just happening in D.C. It's happening everywhere."

Some of these new residential complexes close to jobs may prove enticing to upscale buyers who are tiring of long commutes, said journalist Joel Garreau, author of "Edge City: Life on the New Frontier," a 1991 book that predicted office clusters such as Reston and Tysons Corner would eventually develop more urban amenities.

"The most valuable commodity is always time," said Garreau, a writer and editor for The Post. "It's what we have the most limited amount of -- time. With their long commutes, people have been trading time for a couple of bedrooms."

Even a half-hour commute, along with yard care and pool maintenance, got to be too much for Steven Nowicki, 41, a financial management contractor for the Navy, who traded his ranch-style home in 16th Street Heights in the District for a $420,000 condominium at Langston Lofts, a new project at 14th and V streets NW.

"I didn't really enjoy it anymore," Nowicki said of his single-family house. "It was another thing to take care of, another hassle. . . . I wanted to simplify things."

Nowicki and others are finding their way to a bevy of projects opening up new infill areas in the District to denser residential settlement. According to Delta Associates, more than 9,300 units are being planned for the District, including many in areas that were once crime-ridden and decaying.

"There's been a rebirth of D.C.," said real estate agent Jeff Lockard of Tutt, Taylor & Rankin Real Estate in the District. "Since [former mayor] Marion Barry left office, we saw the city change overnight. Mayor [Anthony] Williams has had a good effect. Everything has changed for the better in the last eight to 10 years. It's made D.C the place to be."

The visible changes are drawing affluent residents to neighborhoods they would not have considered in the past. Stephanie Caputo, 51, a community development analyst with the Office of the Comptroller of the Currency, has lived in the Dupont Circle area since 1988. Next month, she will move to a new $408,000 condominium she has purchased at 2020 12th St. NW.

"I didn't want to be a pioneer in places that were too patchy, too seedy," Caputo said. "I was watching the market, and it wasn't gelling in a way that felt comfortable. I didn't see it coming together -- until it did."

Adaptations of older, sometimes historic, buildings are also attracting interest. One project underway near Union Station, Senate Square, incorporates the old Children's Museum, which is being turned into loft-style condominiums. It will also feature two 12-story towers, with units ranging in price from the high $200,000s to more than $1 million.

Meanwhile, the former Italian Embassy at 2700 16th St. NW is being converted into a complex known as Il Palazzo, where units will cost from $500,000 to more than $2 million. The Silverton used to be the old Canada Dry bottling plant in Silver Spring. The Yale Steam Laundry condos on New York Avenue NW and Parker Flats at Gage School, near Howard University, will both incorporate historic elements into modern buildings.

"There is uniqueness in taking old structures, thinking how to preserve them and how to integrate the new product as well," said Christopher Ballard, president of McWilliams/Ballard, an Alexandria-based residential marketing firm that represents a number of those projects.

Kurtis Brown, 44, a financial analyst for the Administrative Office of the U.S. Courts, found the D.C. market "stale and cookie-cutter" when he moved here from Houston in 1993. Soon he will be moving into Lofts 14, a converted auto dealership at 14th and Church streets NW, with his partner, Charles Griffin, 54, an economist and director at the World Bank. The former industrial space features 15-foot ceilings and wide open spaces that Brown calls "very contemporary and modern." He particularly loves the floor-to-ceiling windows, which he said make the 2,000-square-foot condominium "sun-drenched."

He is thrilled with the lifestyle change ahead. "I'd had a typical nice apartment, but it's nothing like 15-foot ceilings and an open floor plan," Brown said.

On the lower end of the price scale, however, at least 24 apartment complexes in the region have been purchased in the last year for conversion to condominiums.

Penderbrook Square, a golf course community in Fairfax where the units have wood-burning fireplaces and balconies, is being converted into for-sale units with price tags starting at $209,900.

The Four Winds at Oakton is a conversion of the former Summit Square apartment complex, which also features fireplaces and balconies. One-bedroom units there will start in the upper $200,000s.

At projects such as these, developers hope to capitalize on high housing prices that have pushed many buyers out of the market and to make money by offering people homes they can afford.

"These projects fill what we see as an affordability void in the greater Washington, D.C., area," said Christopher Clemente, chairman and chief executive of Reston-based Comstock Homebuilding Cos., when he announced last month that his firm had purchased two apartment properties for sale as condos -- Carter Lake Condominiums in Reston, where prices will start at the mid $200,000s, and Bellmeade Condominiums in Leesburg, where the lowest-priced units will start in the low $100,000s.

Rockville Town Square, now under construction, will feature five condo buildings.

Condo units at Senate Square near Union Station will be priced at up to more than $1 million.

Rockville Town Square amenities will include a library and a shopping center.

Senate Square is a condo project being built near Union Station, on the site of the old Children's Museum. It includes lofts and two high-rise towers.