06/11/2012 03:36 pm ET Updated Jun 11, 2012

World Naked Bike Ride In San Francisco: Naked Bicyclists Advocate Green Living (NSFW PHOTOS)

The ninth annual World Naked Bike Ride took place in the city this past Saturday, and San Franciscans came out in droves to ride bare-bottomed down the streets.

World Naked Bike Ride is an international protest against fossil fuel dependence. "Think of it as critical mass with a really lenient dress code" the website advertises.

This year the ride was a bit smaller than the past, with about 100-120 riders. But it also saw the largest number of female participants thus far. The route took the exhibitionists from Justin Herman Plaza to Golden Gate Park and back, flanked by a large spectator crowd.

Scroll through the slideshow below to witness Saturday's ode to nudity and clean air (warning: graphic photos included):

World Naked Bike Ride