The effect of fast neutron (energy > 0.1 MeV) irradiation on electrical properties and deep level spectra of undoped n-AlGaN films with A1 mole fraction x=0.4 are presented. In virgin samples, the properties are strongly influenced by deep traps at E-c-0.25 eV present in high concentrations (similar to 2.5 X 10(18) cm(-3)). Neutron irradiation with doses higher than 10(15) cm(-2) leads to compensation of these centers with a removal rate of about 500 cm(-1). After neutron irradiation with high dose of 1.7 X 10(17) cm(-2) the samples become resistive (> 10(4) Omega cm), with the Fermi level pinned by new centers near E-c-0.35 eV introduced by irradiation with a rate of about 10 cm(-1). The neutron irradiation also gives rise to an increase of the concentration of deep hole traps with activation energy of 1 eV. (c) 2006 American Vacuum Society.