To characterise insulating materials, measurements of their ability to trap or release injected charges have been developed recently by induced charge measurement (ICM). This new technique allows to investigate the charging properties of bulk or thin oxide films deposited on non-conductive substrates during the electronic irradiation carried out in a scanning electron microscope (SEM). In this work, ICM is used to investigate in MgO single crystal and thin MgO layers deposited on glass or enamel, the effects of substrate, injected charge density and primary electron energy on the kinetics and the nature of the net trapped charge. (C) 2003 Elsevier Science B.V. All rights reserved.