Mattel Inc., maker of Barbie and Hot Wheels toys, said yesterday that its third-quarter profit will miss forecasts by as much as 55 percent because of a huge and unexpected loss at a new educational software unit.

After the announcement, Mattel's stock plummeted in heavy trading, falling 30 percent to close at $11.87 1/2 yesterday on the New York Stock Exchange.

Analysts said the market was reacting not just to yesterday's announcement but also to other problems surrounding the toy industry and Mattel.

Troubles at Toys R Us Inc., the nation's No. 2 toy retailer, have sapped Mattel's sales. And industry observers say today's toys aren't what they used to be. These days, children seem less interested in dolls and more interested in software games--one reason Mattel snapped up the Learning Co., which is second only to Microsoft Corp. in sales of consumer software.

Mattel also announced this spring that it would close some of its facilities and eliminate 10 percent of its work force to reduce costs.

"We have a bit of a double whammy," said Tom Burnett of Merger Insight, an institutional research service based in New York. "Mattel has its own problems, and now the Learning Company, which is supposed to provide [Mattel with] diversification . . . is having difficulty, too."

Mattel said it expects third-quarter sales to drop in the 2 percent to 4 percent range, with net income of 30 cents to 40 cents a share. Analysts surveyed by First Call Corp. had predicted earnings of 67 cents a share.

Mattel acquired the Learning Co., the maker of such consumer software games as "Where in the World Is Carmen Sandiego?," for $3.6 billion in May. It had high hopes, expecting the Cambridge, Mass., company to contribute about $50 million in net income for the quarter ended Sept. 30.

Instead, the new division will hemorrhage between $50 million and $100 million. "It was completely unexpected," said Glenn Bozarth, a spokesman for El Segundo, Calif.-based Mattel. "These matters just came to the attention of Mattel's top management last week, and that's not acceptable."

Mattel blamed the software division's losses on a canceled licensing pact, products returned by retailers and higher promotional costs. The company also said it is owed money from distributors who bring its toys to stores.

Mattel officials provided few details, saying they have not yet gotten all the answers they need from the Learning Co.

"All of these issues are in question, and we have said we're taking a complete review of the Learning Company organization," Bozarth said.

As Mattel puts the heat on the Learning Co.'s management, Mattel's chief executive, Jill Barad, just rated one of the most powerful businesswomen in the United States by Fortune magazine, is also likely to feel the pressure. Barad became CEO in 1997 after years overseeing the company's successful Barbie line.

"I'm sure the board is going to want an explanation," said analyst Burnett.

Even with the cloud over its earnings, Mattel is showing strength in what it is best known for--Barbies, Hot Wheels and Fisher-Price toys. During the quarter, shippable orders of the brands exceeded what Mattel could deliver by more than $100 million.

"Unfortunately, the Learning Company performance masks the underlying vitality of core U.S. business," Barad said.

But the investment community remains cautious about Mattel's future. "We're still trying to figure out the earnings power of the Learning Company, and the impact on Mattel's earnings," said John Taylor, an analyst with Arcadia Investment Corp. in Portland, Ore.

CAPTION: Jill Barad is Mattel's chief executive.