In searches for planetary transits in the field , well over half of the survey stars are typically giants or other stars that are too large to permit straightforward detection of planets .
For all-sky searches of bright V \lesssim 11 stars , the fraction is \sim 90 \% .
We show that the great majority of these contaminants can be removed from the sample by analyzing their reduced proper motions ( RPMs ) : giants have much lower RPMs than dwarfs of the same color .
We use Hipparcos data to design a RPM selection function that eliminates most evolved stars , while rejecting only 9 % of viable transit targets .
Our method can be applied using existing or soon-to-be-released all-sky data to stars V < 12.5 in the northern hemisphere and V < 12 in the south .
The method degrades at fainter magnitudes , but does so gracefully .
For example , at V = 14 it can still be used to eliminate giants redward of V - I \sim 0.95 , that is , the blue edge of the red giant clump .