High energy ion irradiation effects on the transient current behaviour in the range of 0.05-2 s have been investigated. Polyetherimide samples of 25 lain thickness were irradiated with 100 MeV Ag+ beam (fluences: 5.6 x 10(10), 1.8 x 10(11), 1.8 x 10(12) 10(12) ions/cm(2)). The transient currents were obtained in the temperature range 40-250 degrees C for step fields ranging from 40 to 600 kV/cm. The half decay time of the transient currents is field dependent and increases from 0.15 s at 40 kV/cm to 0.30 s at 600 kV/cm. The dipolar relaxation strength, estimated from transient current data, reveals the demerization of carbonyl groups and formation of radiation induced subpolar groups due to irradiation. The charge carrier mobility for pristine and ion irradiated samples at different temperatures and fields have been calculated. The charge carrier mobility is governed by several factors like nature of trapping sites and trap density, crystallinity, backbone conjugation and operating temperature etc. (C) 2008 Elsevier B.V. All rights reserved.