The demonstration - one of several taking place across the country - was the largest since the worldwide protests in February 2003 a month before the invasion of Iraq.

Amid decreasing approval of Bush and widespread disgust over the government's dismal response following Hurricane Katrina, the antiwar movement has revitalized itself.

Crowd estimates ranged from 20,000 to 50,000. Dolores Park was full by noon, and by the time the head of the march reached Market Street, the tail end had not yet left the park.

Saturday's demonstration, sponsored by International ANSWER, brought out a diverse spectrum of Bay Area residents, including student, labor, veterans, religious, queer, and women's groups.

Anarchist Action began a simultaneous demonstration at 16th and Mission, and soon met up with the main march on Dolores Street. Police were out in force, but the day was free of violence.

At the end of the march, at Jefferson Square Park in the Western Addition, an NBC news van was spray-painted and had its window broken. About 20 members of the black block were later arrested while attempting to join the Love Parade, a rave event taking place at Civic Center.