We have undertaken a systematic study of the influence of in-plane crystalline quality of the antiferromagnet on exchange bias. Polarized neutron reflectometry and magnetometry were used to determine the anisotropies of polycrystalline ferromagnetic (F) Fe thin films exchange coupled to antiferromagnetic (AF) untwinned single crystal (110) (formula presented) twinned single crystal (110) (formula presented) thin films and (110) textured polycrystalline (formula presented) thin films. A correlation between the anisotropies of the AF and F thin films with exchange bias was identified. Specifically, when exchange coupling across the F-AF interface introduces an additional anisotropy axis in the F thin film-one perpendicular to the cooling field, the magnetization reversal mechanism is affected (as observed with neutron scattering) and exchange bias is significantly enhanced. © 2002 The American Physical Society.