  We discuss the chiral corrections to f_B and B_B with particular emphasis on
determining the portion of the correction that arises from long distance
physics. For very small pion and kaon masses all of the usual corrections are
truly long distance, while for larger masses the long distance portion
decreases. These chiral corrections have been used to extrapolate lattice
calculations towards the physical region of lighter masses. We show in
particular that the chiral extrapolation is better behaved if only the long
distance portion of the correction is used.
