Nominally a 7+ mile road race from the "bay" (Downtown) to the "breakers" (Ocean Beach), Bay To Breakers exudes the San Francisco spirit in concentrated form - outrageous costumes mixed with a well-poured party. The party includes almost a hundred thousand participants, bands, costumes galore, floats, lots of drinking and overall merriment in a unique and thrilling "anything goes" atmosphere.
There has been increasing chatter amongst higher-ups about cutting down on the partying (and every year there are some that seriously hurt themselves) - enjoy yourself and be safe!
Don't miss the 3rd Sunday in May :)
Website: http://www.baytobreakers.com/
Wikipedia: http://en.wikipedia.org/wiki/Bay_to_breakers