ination mechanism for protons [Hans-84]. This work also investigated track structure effects on charge yield and modeled these effects for protons from 3 to 16 MeV. [Xaps-90] reported a comparison of proton to Co-60 dose response of hardened gate oxides in terms of interface state buildup as measured by the sub-threshold technique. The data did not show a significant difference in response, and their work noted the high value of electric field as being a possible explanation for apparent dose equivalence. There are three implications for the effects of recombination on the charge yield from proton exposures. First, the reduced effect per unit dose suggests that proton studies to assess TID effects should be approached very cautiously, especially if the intended application is in a mixed proton-electron environment, or worse, an environment dominated by electrons. The proton results could lead to slight underestimation of the environment effects. Secondly, if proton dose dominates in the application and the dose response is based on Co-60 studies, they may be slightly conservative. In the absence of detailed proton and Co-60 response comparisons on the parts being considered for flight, good engineering practice argues against factoring the reduced response to protons into the expected part lifetime. Finally, p-MOS dosimeters flown on board satellites may exhibit a reduced response to protons and therefore slightly underestimate the environment, unless the calibration is performed with consideration of the anticipated environment and the energy (and possibly field) dependence of the device response. In summary, to first order, the concept of dose works well for assessing combined effects of various space radiation sources, including protons. In other words, 100 ergs per gram (1 rad) of energy deposition from one radiation source results in approximately the same device response as the same amount of energy deposited from another source. For TID purposes, LNUs from proton exposure do not appear to be an important e