With further miniaturization of the giant magnetoresistive (GMR) heads, the electrostatic discharge (ESD) failure has become the primary reliability issue in manufacturing of these sensors. In this article, the thermal response of the GMR read head to excessive current/voltage during an ESD event is investigated numerically, using a three-dimensional (3D) finite element analysis. Unlike the previous studies, the thermal properties of the GMR, Al2O3 gap, and shield layers used in the simulation are the experimentally measured values, which are different from the bulk values. The simulation results show that temperature in the GMR element sharply increases as the GMR dimensions are reduced, indicating the future GMR heads will be more susceptible to the ESD damages. In addition, thermal properties of the GMR elements and the gap materials play key roles in the accurate prediction of the temperature field in a GMR head during ESD events. The simulations are performed for both the current-in-plane (CIP) and perpendicular-to-plane configurations, indicating that latter can sustain much higher ESD voltage (∼160 V) than the CIP-GMR head (∼48 V) for 100 Gbits/in.2 recording density. © 2004 American Institute of Physics.