America Online Inc. soon will face the first test of investor confidence in its recently announced marriage to Time Warner Inc.

As AOL stock continues to swoon while shareholders remain jittery and unsure about how to value the merger--shares have fallen about 18 percent since Jan. 10--some investors of MapQuest.com Inc. are watching with trepidation.

That's because AOL announced in late December that it was acquiring MapQuest, of New York, in an all-stock transaction. At the time, AOL stock traded at about $85 and the deal was valued at about $1.1 billion. But yesterday, less than a month later, AOL shares closed at $60.50 and the value of the deal had shrunk to about $785 million.

Technically, such deals are subject to shareholder approval. Investors have a right to block the deal if they feel it is not in their best interest, as they did a proposed merger between Lycos and USA Networks Inc.'s Home Shopping Network in early 1999. And typically, acquisition agreements contain "collars" on the stock price, which protect investors from such large fluctuations by changing the terms of the deal depending on the value of the shares.

But the MapQuest and AOL attorneys who drafted the agreement, expected to close this spring, decided against a collar. Robert McCormack, managing director of Trident Capital--MapQuest's major investor, with 33.3 percent of its stock--said he did not insist on a collar because he had not expected AOL stock to drop so rapidly.

"It was a very lengthy discussion with AOL and they thought there was a greater risk of their stock price going up than down, and we agreed that it had more upside than downside, so we didn't put it in the agreement," he said.

McCormack said he would not rule out the possibility of terminating the deal if AOL's stock sinks further--although he emphasized that he is not yet concerned.

The venture capitalists who nurtured MapQuest still own more than 70 percent of its stock and have pledged their support to the acquisition. Even a "no" vote from all the public shareholders would have only a symbolic impact.

So far, some small investors, already unhappy that MapQuest is being sold to AOL, have not taken the news of the Time Warner deal well. On the three days that followed the Jan. 10 announcement of the merger, more than 3 million shares changed hands, more than triple the normal activity, and MapQuest shares have fallen 19 percent since the announcement, closing at $18.25 yesterday.

"The potential of [MapQuest] was right up there with Yahoo in my mind," said Dale Platteter, a shareholder from Bedford, Ind., who sold his stock right after the Time Warner announcement. "But they did what they did, and you dump your shares and move on."

Others, who hadn't moved quickly enough to sell before MapQuest shares fell, have filled Internet message boards with messages of frustration, lamenting how they had bet on a highflying Internet stock and are now potentially stuck with the more stable but slower-growing blue-chip stock of a media conglomerate.

"To the VC and Funds that support the buyout by AOL: . . . You were downright STUPID to support this buyout deal without tighter provisions," read one note on the Yahoo online finance board.

Thuan Nguyen of Falls Church considers himself one of the lucky ones. When he heard news of the AOL-Time Warner deal on the morning of Jan. 10, he immediately got rid of his 350 shares of MapQuest.

"Short-term and long-term potential is now nil because they are swallowed in AOL. Other portal sites that compete with AOL will be hesitant to use MapQuest service," said Nguyen, a 34-year-old software engineer.

AOL's acquisition of MapQuest is also being challenged by one of the mapmaker's competitors, Universal Map Enterprises Inc. of Lansing, Mich., which filed a federal lawsuit Friday seeking to block the deal. Universal Map alleges that MapQuest.com had agreed to sell the Web site MapStore.com, which sells print maps and other items, to Universal Map and that it reneged on the sale within 24 hours of the AOL announcement.

AOL officials referred all calls to MapQuest. A MapQuest spokeswoman said the company "is confident that there is no risk of any injunction with the merger" but declined to talk about the allegations in the suit and about how AOL's falling stock prices might affect the pending acquisition.

Ulric Weil, senior technology analyst at Friedman, Billings, Ramsey Group Inc. in Arlington, predicted that concern over the MapQuest deal will soon disappear and that AOL stock will rebound, especially after AOL announces what are predicted to be rosy quarterly earnings this afternoon.

If MapQuest "shareholders really look at the Time Warner deal, they say we are jumping into a bigger pond, and that can only be a good thing," Weil said.

Staff researcher Richard Drezen contributed to this report.