NEW YORK (AP) _ Media Metrix Inc. is buying Jupiter Communications Inc. in a $400 million all-stock deal that creates a giant Internet research and audience tracking company.

The new company will be called Jupiter Media Metrix and will have more than 1,700 clients worldwide, including some of the biggest technology companies, advertising agencies and media firms.

Media Metrix tracks how many people visit sites on the Internet. Jupiter is a consulting and research firm that does in-depth reports on the state of the Internet industry and economy.

The companies said the merger will help them expand into international markets faster and also give them an edge over their competitors, none of which offer as broad an array of Internet-related data. Their rivals include Nielsen Net Ratings and Forrester Research.

The new company is expected to be profitable by the fourth quarter of this year.

Under the deal announced Tuesday, Jupiter shareholders will receive 0.946 shares of Media Metrix for each share held.

Media Metrix chairman and chief executive Tod Johnson will remain at the helm of the new company. Gene DeRose, chairman and chief executive of Jupiter, will serve as president and vice chairman.

Question about how the companies would integrate their businesses pushed Media Metrix shares down $3.125, or 11 percent, to $25.125 in afternoon trading on the Nasdaq Stock Market. Jupiter's stock was unchanged at $23, also on the Nasdaq.

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On the Net:

http://www.mediametrix.com

http://www.jupitercommunications.com