And when Mr. Bush's motorcade rolled right past them on Pennsylvania Avenue at Fourth Street shortly after 3 p.m., they let him have it with all the invective they could muster.

"Racist, sexist, antigay. Bush and Cheney, go away."

That was one chant from the largest crowd of demonstrators on the parade route as Mr. Bush passed. Through the darkened windows of his limousine, it appeared that he and Mrs. Bush were waving to the crowd anyway.

At least 13 people were arrested by late Thursday night after a variety of incidents, some far from the parade route, which took the presidential party from the Capitol to the White House. At least one woman, naked but for red, white and blue underpants, was hustled off Pennsylvania Avenue near 12th Street by the authorities, and several demonstrators (fully clothed) were driven back from barricades by pepper spray near Seventh Street and taken into custody.

But none of the incidents dampened the mood of protest organizers who declared the day a resounding success.

"We think this is a significant achievement for the antiwar movement," said Brian Becker, national coordinator of a protest coalition called Act Now to Stop the War and End Racism, or Answer. "We have bleachers, a stage, a sound system, and we're right along the parade route. We feel we have succeeded."

Never before had the Park Service granted a protest group dedicated space for the inaugural parade, organizers said, and Mr. Becker's coalition filled it with thousands of people who were as close to Mr. Bush as those who came to cheer him.

For hours before the procession began, they waited in the cold, listening to a succession of speakers who complained about administration policies involving Cuba, Iran, housing, Venezuela, health care, jobs, Social Security, same-sex marriage, Afghanistan and North Korea.

But mostly the tirades, as well as the signs and banners, attacked the administration for its involvement in Iraq. One sign read, "How many lives per gallon?" Another said, "Who would Jesus bomb?" Yet another said, "Torture is not a moral value." One more: "Iraq. Tomb of the Unknown Exit Strategy."

Ramsey Clark, an antiwar figure who served as attorney general under President Lyndon B. Johnson, appeared early and told the crowd that the Bush administration had "made the world a more dangerous place."

"It's because of what we've done and what we're doing right now," Mr. Clark said, adding, "Impeachment now is essential to the integrity of the U.S. government and the people of the United States."

While the protesters mixed with Bush supporters in many other areas along the parade route, no place had a bigger concentration than the Fourth Street location, within sight of Mr. Bush's swearing in. It quickly became a fault line of American political sentiment as ticketholders from the swearing-in ceremony just blocks away walked through a gantlet of tormentors in search of their seats for the parade.

One man wearing anti-Bush buttons screamed, "Scum," into the ear of an elderly woman, a Bush supporter. The man walking behind her punched him in the face. Some of the Bush supporters laughed off the taunting; others looked terrified.

The numbers of protesters along Pennsylvania Avenue might have been greater, but the swarm of people trying to pass through security checkpoints made it hard to reach the parade route quickly.

Bill Wolf, 47, a protester from Ringoes, N.J., who carried a sign that said, "War Mongers," said he had waited in line an hour to get in.

"It's overkill to the extreme," he said about the procedure. "I think it was designed specifically to suppress dissent and keep out protesters. They want to control the visual image as part of an effort to mislead the American people about the level of opposition to this administration. They're trying to make it a coronation, and it's not."