Letterman to reveal Sports Illustrated's Swimsuit Issue tonight

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For the third year in a row, David Letterman will have the honor of unveiling the cover of this year's Sports Illustrated Swimsuit Issue. The model and the cover itself – both kept under tight security until the big reveal tonight – will appear on the "Late Show with David Letterman," airing at 11:35 p.m. EST.

Last year's cover girl was Bar Refaeli, the Israeli model and on-again-off-again girlfriend of Leonardo DiCaprio.

Former cover girls include Tyra Banks, Rachel Hunter, Kathy Ireland and Elle Macpherson. Check out SI's gallery of past Swimsuit Issues from 1964-2009 here.