NEW YORK -- VNU NV, the Dutch media company that has quietly built a publishing powerhouse in the U.S., said it plans to buy Nielsen Media Research Inc., the television-ratings service, for $2.5 billion plus assumption of $200 million in debt.

The deal gives VNU one of the most high-profile names in American media. Though Nielsen has been a stand-alone public company only for the past year -- it was previously part of Cognizant Corp. -- the company has dominated the business of audience counting since 1936, when it started in radio, before moving on to television.

Today, Nielsen's ratings data -- compiled in part by people who fill out television-watching diaries in their homes -- are used by network executives to decide what gets on the air, and by advertising agencies in determining where to place their commercials. Nielsen in recent months also has moved to expand its ratings expertise to measuring Internet usage, a move that has caused analysts to boost their expectations for the company.

Speeding Up the Transition

VNU executives said they hoped the company's largest acquisition ever would speed up VNU's transition from mostly a trade publisher into a full-blown information and research concern, with an expanding Nielsen Internet presence. In addition to a print stable that ranges from the Hollywood Reporter and Adweek to Billboard and Convenience Store News, VNU in the U.S. also sells consumer data to ad agencies and consumer-products companies. U.S. revenue last year totaled $751 million, accounting for about 29% of the company's total. VNU, which stands for Verenigde Nederlandse Uitgeversbedrijven BV, is based in Haarlem, the Netherlands.

Under its definitive agreement with Nielsen, VNU will pay $37.75 a share for Nielsen stock. While that represents a 15% premium over Nielsen's closing price on Friday -- the last trading day before the deal was announced -- it nevertheless was criticized by some analysts, who felt that Nielsen could have fetched a higher price. "Personally, I'm a little disappointed," said Monica Logani, an analyst at Lehman Brothers. in New York. "I don't think they're getting enough for their core business."