This study presents an experimental analysis of the Xray radiation effect on the drain induced barrier lowering (OIBL) of strained and unstrained, p and n type triple gate SOI MuGFETs. In both types of devices, the narrow fin transistors are more immune to radiation because of the better coupling among the gates. It is shown that total dose damage in nMuGFETs always leads to a performance degradation, based on the subthreshold region characteristics studied. For pMuGFETs, radiation is not always harmful, because it reduces the leakage current, improving the subthreshold swing of the drain current. However, for devices that are less sensitive to this leakage current, the radiation-induced interface traps become the predominant damage mechanism.