SAN FRANCISCO -- After hours of peaceful revelry, violence broke out early Tuesday as hundreds of San Francisco police officers moved in to break up the annual Halloween celebration on Castro Street.

There were several fights, 12 arrests and one man was stabbed at Castro and 18th.

Earlier in the evening, thousands of revelers came out for a well-behaved Halloween celebration in the Castro with people dressed as Adam and Eve, Jedi knights and even an iPod.

Vincent Roy, 34, of San Francisco, dressed up for the first time at the city's gay and lesbian community's massive Halloween street party. He wore a cardboard iPod costume that played dance tunes when people pushed a play button.

"I like dressing up because you can be something you're not," Roy said. "No one knows who I am. I am anonymous."

There was a large police presence at the parade to prevent a reoccurrence of the events of three years ago, when officials recorded five stabbings and a number of assaults in a crowd of 500,000. A chain saw also was confiscated during that event.

The once-spontaneous and unsanctioned party is now run by the city and police randomly searched people as they came through the 18 entrance gates. Organizers expected about 200,000 people to attend the parade, which was peaceful.

Music could be heard for blocks and many people came to gawk -- dressed in street clothes and taking pictures of those in costumes. It was a family affair for some, as parents came with their children.

There were even some three-generation groups, including Tricia Day's family, which dressed up as the cast from Batman.

"It's Mardi Gras in San Francisco," said Day, a 50-year-old from Baton Rouge, La. "It has much the same atmosphere but there are more sober people."

Day, who was in town with her husband visiting their son's family, was dressed as the Penguin, while the rest of the family dressed as Batman, Joker, Catwoman and a six-month old Robin.

Mike Bories, 43, came straight home from work to attend the parade in his neighborhood, although he wasn't dressed up.

"I just got sucked into the crowd. I love it," said Bories, who has been attending the parade for 15 years. "I like the sense of community. Everybody from the Bay Area comes out."