To Aleksandar Vajsel, the crowd of casually dressed men and women on the other end of the bridge is a lynch mob waiting to burn him out of his apartment and expel him from Kosovo. Though none wears a uniform, Vajsel has no doubt they are armed members of the rebel ethnic Albanian army.

He stands in the street, along with other men, ready to defend himself. Many of the men carry iron bars and wooden clubs. At any sign of movement on the other side, they fan out and surge forward against a line of blue-shirted French gendarmerie and flak-jacketed French army troops.

For all the nationalist music and tough talk of fighting to the last man, fear is the predominant emotion on this side of the bridge. Vajsel is among the dwindling number of ethnic Serbs in Kosovo, and he thinks about that every waking moment.

Wrenched from superior status, they are increasingly lonely and resentful of the changes transforming this Serbian province. Though they were only 10 percent of its population before the war, Kosovo's Serbs ruled. Now they face a dilemma: Should they stay or should they leave for the security of more hospitable ethnic surroundings? If they decide to make a stand in Kosovo, where coexistence with the ethnic Albanian majority seems improbable to many, what would they gain?

At least 50,000 ethnic Serbs -- and perhaps as many as 100,000 -- have already decided. They have stuffed all their belongings into trailers, hitched them to complaining Lada and Zastava automobiles and headed north in slow-moving convoys.

By so doing, these lifelong Kosovo residents have rejected the appeals of NATO officials and Western political leaders, who have traveled here to say that they want to preserve Kosovo's multiethnic character. These remaining Serbs also found no solace in the U.N. Security Council's pledge to safeguard the interests of all civilians.

They also spurned the appeals and orders of the Serb-dominated government in Belgrade, which wants to fend off a surge of refugees when it cannot adequately house, feed or employ its present residents.

There is no single explanation for the Serbs' flight. Some express general anxiety about losing the privileges they've enjoyed since 1989, when Yugoslav President Slobodan Milosevic fired hundreds of thousands of ethnic Albanians from government jobs. Some Serbs doubtlessly have guilty consciences and fear reprisals or arrest, having joined in the rampage of Serbian security forces against civilians while NATO conducted its airstrikes.

But others say they are pulling out because their neighbors are, because their surroundings aren't familiar anymore and because they don't want to be the last Serbs holding on here.

Their reasons for leaving are not hard to fathom. As Vajsel, 34, and his friends look around the burned and looted landscape left by Yugoslav troops, they don't see Yugoslav flags on public buildings or any other signs of Yugoslav sovereignty. They cannot switch on any Serbian broadcast outlets, and they cannot find any popular Serbian daily newspapers. They listen, out of curiousity and a thirst for information, to the Voice of America.

When they wander the streets of their area of Kosovska Mitrovica, they cannot find a functioning city government run by ethnic Serbs, one ready to put Serbs ahead of others in line for scarce services. With the city's economic life almost at a standstill, there are very few open Serbian shops, bars and restaurants. There is no Yugoslav army and no Serbian police. There are French-speaking NATO troops for protection but until two weeks ago, warplanes controlled by the same alliance were dropping bombs on Serbs all over Yugoslavia.

The Serb-run University of Metallurgy has closed. The University of Pristina in the provincial capital south of here has lost most of its ethnic Serbian faculty. The local hospital is under heavy pressure to rehire ethnic Albanians who were fired or forced out during recent ethnic strife.

The Serbs who gather here to peer through binoculars at the ethnic Albanians at the other end of the bridge -- past the orange hulk of a burned-out car -- say they have few comforts now. They have the pride that comes from standing together here. And they have music, which they play loudly from speakers in the trunk of an old car. "Ziveli Srbi; Zivela Srbija," the folk singer intones. "Long live Serbs, Long live Serbia."

The ethnic Albanians across the bridge say they are simply waiting to get to their homes and jobs on the Serbian side of the bridge. They say the crowd of Serbs includes paramilitaries who torched, bulldozed or bombed almost all of Kosovska Mitrovica's ethnic Albanian commercial district before the Yugoslav military withdrew from Kosovo. They complain that only women and children have been allowed to cross the bridge, and that some were beaten when they did.

On the Serbian side, however, David Ordic, 19, said: "We are afraid of the Albanians. They want to control this town. . . . Look over there. That part of the town has all Albanian flags. The KLA has all the army, all the police stations. We have nothing."

Vajsel, who worked at the nearby Trepce mine, agreed. "They left us all alone here. All the institutions are on the other side of the bridge. The mine is under KLA control and we are jobless now."

Velijko Jovanovic, 26, a University of Pristina law student, said the Serbs' growing isolation in Kosovo is a bitter pill after three wars in the past decade carved away other parts of Yugoslavia. He said most of the remaining Serbs live in just six Kosovo cities and towns: Kosovska Mitrovica, Kosovo Polje, Lipljan, Gracanica, Preluzha and the center of Pristina.

But he has not been to Pristina since the war ended; its center is now crowded with ethnic Albanians who have taken over Serbian cafes. At the University of Pristina, moreover, only graffiti marks it as a Serbian institution. About three-quarters of the Serbian faculty fled in the past two days, apparently frightened by the torture and execution-style slaying Wednesday of economics professor Milan Lekovic and the kidnapping Monday at nearby Pristina hospital of a Serbian physician, Andrija Tomanovic, well known for his hard-line views.

Vojislav Jovanovic, 37, an assistant professor of biochemistry at the university, watched several colleagues drive away this afternoon, and said: "I feel pretty desperate. . . . I wish that things would be different, that the time before 24 March [the start of NATO airstrikes] will come back. But I know it will be very hard. I have very little left that makes me feel comfortable -- mostly just talking to my daughter, who has been in Nis [a city outside Kosovo] since then."

NATO officials have deployed a squad of British paratroopers at Serbian faculty apartments to ensure their security and discourage their leaving. Senior NATO officials, including British Brig. Gen. Jonathan Bailey, went there this morning to try to persuade some to stay.

"I told them thousands of Serbs have died for your country, and you're leaving because you're scared," he said. "I told them I thought that was rather feeble behavior. I was trying to provoke them and embarrass them. It didn't work."