SAN FRANCISCO and LOS ANGELES — After months of speculation, LoopNet and PropertyFirst.com have merged. The move sets up an epic battle for Internet dominance against Bethesda, Md.-based CoStar Group, the industry’s current 800-pound gorilla.

The new company will operate as LoopNet, offering more than 145,000 sale and lease listings. The companies will integrate operations including Web sites, data and customer bases.

"The commercial real estate industry may well be at an inflection point. In fact, we’re betting on it," said John Stanfill, president and CEO of PropertyFirst. "With this merger, we’re saying there needs to be a reduction in marketplace confusion and a clear, strong winner for our customers."

Added LoopNet CEO Dennis DeAndre, "The merger is a natural step for both companies. Both firms are rapidly gaining customers and traction, but the combined company will be even stronger."

DeAndre and Stanfill will serve as co-chairmen of the new company, which will operate with two principal offices, in San Francisco, where DeAndre will be based, and Los Angeles, where Stanfill will be located. The company will be governed by a new board of directors that includes equal representation from the two former firms.

Morgan Stanley Dean Witter advised LoopNet in the transaction, while JPMorgan advised PropertyFirst.com.