Radiation‐induced conduction in polyethylene‐terephthalate (PET) has been measured under high electric field (1.0×106to 1.6×108V/m). In a 6‐&mgr;m‐thick PET film, saturation of the radiation‐induced current occurs at field strengths above 1.2×108V/m. This has been demonstrated by the thickness and dose rate dependence of the induced current. Radiation‐induced conductivity increases monotonically with field strength, then shows a saturation tendency. This may be explained by geminate recombination. Above 1×108V/m, slowly increasing radiation‐induced current appears. This may be caused by electron injection from the cathode, enhanced by the accumulation of the hetero space charges near it.