Thousands of cyclists descended upon San Francisco on Friday for the 20th anniversary of Critical Mass--a global biking event.

Riders wore costumes and included families, bike messengers and cycling enthusiasts for an evening ride across the city. Motor traffic was, as predicted, snarled.

Did you attend the ride? Let us know how it went in the comment section. In the meantime, check out some photos from the event in the slideshow below:

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  • <em><a href="http://www.flickr.com/photos/cristi4nov4lli/8034628745/">Photo courtesy Flickr: [c]*</a></em>

  • <em><a href="http://www.flickr.com/photos/sixteenmilesofstring/8034368552/">Photo courtesy Flickr: tvol</a></em>

  • <em>Photo courtesy <a href="http://www.flickr.com/photos/cristi4nov4lli/8034626246/">Flickr: [c]*</a></em>

  • <em>Photo courtesy <a href="http://www.flickr.com/photos/cristi4nov4lli/8034627630/">Flickr: [c]*</a></em>

  • <em><a href="http://www.flickr.com/photos/cristi4nov4lli/">Photo courtesy Flickr: [c]*</a></em>

  • <em><a href="http://www.flickr.com/photos/cristi4nov4lli/8034627609/in/photostream">Photo courtesy Flickr: [c]*</a></em>

  • <em><a href="http://www.flickr.com/photos/kristiewells/">Photo courtesy Flickr: kristiewells</a></em>

  • <em><a href="http://www.flickr.com/photos/telstar/8034727290/">Photo courtesy Flickr: Telstar Logistics</a></em>

  • <em><a href="http://www.flickr.com/photos/kristiewells/8035963066/">Photo courtesy Flickr: kristiewells</a></em>

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