Radiation‐induced conduction in polyethylene‐terephthalate under high electric field (1×106to 1.6×108V/m) has been studied. At field strengths below 1×108V/m, the induced current reaches its initial steady‐state value (primary component) soon after irradiation is initiated, then monotonically decreases with time thereafter. This decrease of current is due to a ’’polarization’’ effect. Above 1×108V/m, the induced current decreases for a while then increases again to reach the equilibrium value (secondary component). This secondary component is due to the electron injection, enhanced by the fixed positive space‐charge accumulation near the cathode. The radiation‐induced conductivity of the primary component increases with electric field strength between 1×106and 1×108V/m and then shows a saturation tendency above 1×108V/m. This may be due to geminate recombination in the carrier generation process. The primary component in the 50‐&mgr;m‐thick specimen is deduced to be dominated by a deep‐trapping‐limited process. The primary component of the induced current in a 6‐&mgr;m‐thick specimen is demonstrated to attain saturation above 1.2×108V/m.