  We present results of a study of the localization capability of Fermi-LAT,
using a large set of blazars with precise radio locations. Since the width of
the PSF decreases with energy, the performance is typically dominated by a few
high energy photons, so it is important to properly characterize the
high-energy PSF. Using such data, we have found a need to modify the pre-launch
high-energy (greater than a few GeV) PSF derived from extensive Monte Carlo
simulations of particle interactions in the LAT; the resulting data-based PSF
is shown
