The authors report on improved methodologies of predicting upset rates of sensitive devices for neutron energies less than 20 MeV and between 20 and 50 MeV in silicon and apply these to predicting the neutron-induced single-event upset (NSEU) in the atmosphere for one of the most SEU-sensitive LSI bipolar RAMs (93L422). The improved method uses the differential cross section in both energy and angle from the most recent Evaluated Neutron Data File (ENDF-V), an extrapolation of the ENDF data to neutron energies in the 20-50-MeV range, and the detailed energy and angular dependence of the energy deposited as ionization in the sensitive volume of the device. The revised conclusions principally are: (a) elastic scattering contribution is reduced from that predicted by previous methods by an energy-dependent factor approaching an order of magnitude at 19 MeV; (b) the contribution due to inelastic scattering processes is dominant, particularly for neutron energies above 10 MeV, as opposed to dominance by the elastic scattering predicted previously; and (c) the previously neglected alpha particle contribution in (n,alpha) reactions is significant for critical charges >