Recent results from the HARP experiment are presented.  The
double-differential production cross-sections of positive and negative
pions resulting from proton interactions with a wide variety of nuclear
targets are shown. Results include production at small angles (30-210
mrad) with high momenta up to 8 GeV/c and at large angles (0.35-2.15
rad) and low momenta (0.1 - 0.8 GeV/c).  These HARP pion production
cross-sections contribute directly to the understanding of neutrino
fluxes in accelerator based neutrino experiments, provide insight into
the optimization of neutrino factory designs, enable better prediction
of atmospheric neutrino fluxes, and facilitate the improvement of
hadronic generators currently used in the simulation of hadronic
interactions.