Let JAMI SECCHI, who tenaciously researched the local real estate market even after she and her husband, Marc, had bought a house in Dix Hills and were about to move in, got a surprise when she logged onto the Multiple Listing Service of Long Island Web site in mid-July.

She found that the service had expanded the information available to the public, offering recent sales prices, complete with maps, addresses and photos of sold homes.

She searched the Web site for data on Dix Hills and found that a house down the block from the one she and her husband bought had been sold. “We were already in contract at the time,” Ms. Secchi said. “But I had been curious for weeks about what that house sold for.”

It was a relief to learn that they had been “in the ballpark” with their bid, Ms. Secchi said. “You don’t want to see that a house sold for $50,000 less if it’s a similar house.” The listing service, a real estate professionals’ organization with more than 23,500 members in Suffolk, Nassau and Queens, has traditionally provided the public with data only about homes for sale; its Web site has been a tightly controlled portal to what is considered the largest database of Long Island residential real estate listings.

The increased Web offerings seem to reflect a new awareness among listing service officials that much of their data has for several years been available in bits and pieces to Internet searchers via other Web sites — for instance Trulia, Zillow, Propertyshark, Realtytrac and most major newspaper sites.

“If we know that they can get the information anyway, why send them somewhere else to get it?” said Barbara Ford, president of the Multiple Listing Service of Long Island. Earlier this year, she added, the service added rentals to its search engine. Before the end of the year, it also plans to add homes in the foreclosure process, she said.

Brokers are required to update the listing service’s Web site within 48 hours of a sale, Ms. Ford said. That is far ahead of most other Internet tools, which rely on the listing service and other sources to provide them periodically with data. Zillow, for example, publishes recent sale prices from county records.

In Nassau and Suffolk counties, the median time for a sale to be recorded is 37 days, according to Amy Bohutinsky, a Zillow spokeswoman. Recent sale prices on Trulia are not updated until one to three months after a sale is completed, the company reported.

On the listing service site, Ms. Ford said, “you’re getting information as it occurs. Under current market conditions, a buyer or seller wants to know what’s happening now, not six months ago or a year ago.”

But even though brokers visit the Web site to update and consult it, more than a few hadn’t realized by late July that the general public now had access to the sold-homes data.

“I’m not thrilled about it,” said Donna Galinsky, a broker with Pugatch Realty in Valley Stream upon learning of the addition from a reporter. She explained that because buyers and sellers often “don’t know the difference between property A and property B,” the added data provided by the Web site might increase the challenges for a broker trying to explain why one house is worth, say, $20,000 more than another.

Referring to sales and foreclosure records, Ms. Galinsky added: “It’s there, it’s truth, it’s public record. There’s nothing wrong with an educated consumer.”

But overseeing that consumer’s education has more appeal — which is why Ms. Galinsky has been providing her clients access to yet another new Web site, Listingbook. Like the other sites, it uses Multiple Listing Service data. But with brokers as its gatekeepers, it is not directly accessible to the public.

After Ms. Galinsky grants a client access, Listingbook notifies her when that client shows interest in a listing, or a neighborhood, or a price range. “I can see what they’re looking at, their likes and dislikes,” Ms. Galinsky said of the big-brotherly view she gains.

Since the site became available in Long Island and Queens last November, she and about 7,000 other area brokers have signed up about 20,000 buyers and sellers to Listingbook by means of an e-mail initiation message, said James Barry, president of Listingbook, based in Greensboro, N.C. (The site is viable only in areas whose listing services offer very robust storehouses of data. So far, those areas include Southern California, Detroit, and parts of Florida, as well as Long Island.)

One of Ms. Galinsky’s clients, Jennifer Membreño, has been using Listingbook almost exclusively since she first signed up to sell her two-bedroom co-op in Fresh Meadows, Queens, where she lives with her husband, Oscar, and their young daughter, and to search for a new house in Nassau County.

She used Listingbook to help set the price on her co-op. “I looked at what other places are selling for, and at the balance on my mortgage, and listed it at a bit less than what the others were asking,” Ms. Membreño said. Thus, when Ms. Galinsky came to her apartment to estimate the sale price, she found Ms. Membreño’s price of $215,000 about right.

Ms. Secchi too was granted access to Listingbook, which she found useful for its automatic e-mail messages each time a price was lowered on a house she was interested in, or when the house had an accepted offer.

With her near-obsessive interest in what’s selling and for how much in Long Island’s real estate market, Ms. Secchi said she had seriously considered whether she needed a broker to sell her house. Such yearnings for independence may be why brokers like Ms. Galinsky prefer to control the amount of information available to their clients.

But paradoxically, given today’s credit crisis and tighter lender restrictions, brokers should probably feel more sanguine rather than less — despite clients’ increased access to information. As Ms. Secchi acknowledged, she needs help confronting prospective buyers in this climate. “I was worried about the type of buyer coming in, and his financial history,” Ms. Secchi said. “How can I evaluate that? Can I ask for his credit report?”