Scantily clad Santas will once again bare almost all down Boylston Street for the annual Santa Speedo Run this Saturday. With easily more than 500 participants, the fun starts at 10 a.m. at Lir Tavern with check-in. 

The 1-mile run starts at the tavern, at 903 Boylston St., at 1 p.m. and then heads down Boylston to Berkeley, up Newbury to Gloucester and back to Lir Tavern. 

If you're feeling nostalgic, or want to know what you're getting yourself into, check out the photos from 2010 or those from 2011.

If you want to run, note that Friday is the last day to pre-register. Do so from 4 p.m. to 8 p.m. at City Sports, 480 Boylston St.

Proceeds will support the Play Ball Foundation, which funds after-schools sports for Boston Public Schools. 

And while you're at the run don't forget to check out the Newbury Street Holiday Stroll from noon to 4 p.m.