NEW YORK - First the dot-coms blew up. Then the stock market tanked. Now New Yorkers are worried that their bedrock investment - their homes, which have skyrocketed in value over the past few years - might be the next bubble to burst. working in the world's financial capital, as would any young man right out of college.

''There's anxiety out there,'' said Barbara Corcoran, chairman of the Corcoran Group, one of the city's largest real estate companies. ''And anxieties create a slow market.''

''The bubble isn't about to burst - it's bursting,'' said M. Myers Mermel, chief executive officer of TenantWise.com, which monitors the city's real estate trends.

While some would not go that far, the trends seem grim.

In Manhattan, where the rise has been steepest, sales volume this autumn for upper-middle-class units - condos and co-ops listed at about $600,000 - has declined by 20 percent.

In more expensive neighborhoods, with units priced at $2.5 million or more - and there are hundreds of townhouses and apartments that sell for this much each year - volume is off 30 percent.

At the high end, where prices exceed $20 million, the market is at a standstill. There are 25 of these urban palaces on the market now. Usually, there are two or three.

''In real estate, when people are worried, they don't do anything,'' Corcoran said. ''We're in the equivalent of a bear market. It's stagnant.''

In June, the average home for sale stayed on the market for 66 days. Last month, the figure rose to 71 days.

Leslie J. Garfield, a real estate agent who deals primarily in high-end properties, said, ''In Park Avenue buildings that have seven- or eight-room apartments, normally we see one apartment up for sale. Now, in many of these buildings, we see three for sale.''

Mermel said the big worry is not so much plunging prices as their cascading effects. Owners have leveraged the equity value of their homes to take out massive loans. If the price - and therefore the equity value - drops, the banks might call in the loans.

A few years ago, this might not have been a problem. Executives in the financial sector - where most multimillion-dollar homeowners work - received year-end bonuses equal to their annual salaries. The recession has cut these bonuses severely, in many cases ending them.

''A lot of bankers are worried that they're going to get a lot of loan defaults,'' Mermel said.

But Garfield, Corcoran, and other realtors and appraisers - while foreseeing prices continuing to fall - do not expect a crash.

''Is there some bubble about to burst?'' Garfield asked. ''No, I don't think so.''

They say that this autumn seems particularly stagnant because it followed a record summer caused by three events. First was the release of pent-up demand, and a general relaxation, after the Sept. 11, 2001, terrorist attacks.

Second, people got out of the stockmarket and found themselves with huge amounts of cash. ''They lost money, but they liquidated,'' Corcoran said. ''What were they going to do with it - put it in the bond market?''

Third, mortgage-interest rates plummeted.

The biggest boost, as a result of this last factor, took place in the lower end of the housing market - studio and one-bedroom apartments, which in Manhattan cost from $300,000 to $500,000.

''A lot of renters decided to go buy,'' Corcoran said. ''In fact, the hardest-hit market has been rentals. Volume and prices are down much more in rentals than in sales.''

Jonathan Miller, president of Miller Samuel Inc., a real estate appraising firm, said, ''A high level of activity is continuing in the entry- to mid-level of the housing market.''

He also noted that, even in the expensive markets, while volume is lower than it was last summer, it is considerably higher than at this time last year.

Manhattan real estate has been through crashes before. In the late 1980s and early '90s, prices fell by as much as half.

However, the years that preceded the crash were fueled by tax shelters that let brokers make a fortune in ''condo-flipping'' - rapidly buying then selling condominiums. Corcoran recalled that, during those years, one-fifth of her business was done with condo-flippers.

Then tax reforms closed the shelters, and the market collapsed. It didn't help that New York City was, at the same time, going through a recession, a crack epidemic, a crime wave, a tax hike, and - as a result of all these problems - a middle-class exodus.

Today, crime seems to be well under control, but the city is facing a huge deficit and unemployment is approaching 8 percent.

''I think what we're seeing in housing now is a pause, like we've seen many times before,'' Corcoran said. ''I think the market will come back. But if there's a national economic crisis or another terrorist attack or a war - then I'll be more worried.''