A new technique is proposed to evaluate the radiation response of metal‐oxide‐semiconductor (MOS) transistors. The method requires that otherwise identicaln‐ andp‐channel transistors be irradiated under the same conditions. Using assumptions similar to those of widely accepted ‘‘single‐transistor’’ methods, standard threshold‐voltage and mobility measurements are combined to accurately estimate threshold‐voltage shifts due to oxide‐trapped charge and interface traps. This approach is verified for several MOS processes. The dual‐transistor method can be applied to devices with much larger parasitic leakage, and at shorter times following a radiation pulse, than subthreshold current or charge‐pumping techniques.