We report on recent studies of the effects of 50 keV focused ion beam (FIB) exposure on MOS transistors. We demonstrate that the changes in transistor parameters (such as threshold voltage, Vt) are essentially the same for exposure to a Ga+ ion beam at 30 and 50 keV under the same exposure conditions. We characterize the effects of FIB exposure on test transistors fabricated in both 0.5 μm and 0.225 μm technologies from two different vendors. We report on the effectiveness of overlying metal layers in screening MOS transistors from FIB-induced damage and examine the importance of ion dose rate and the physical dimensions of the exposed area.