Negligible reversible changes in magnetic properties of thin metallic films exhibiting high Curie temperatures are expected over normally encountered temperature ranges. However, irreversible changes of the magnetic properties of vacuum-deposited films have been observed when they are subjected to high magnetic fields at temperatures in the order of 100°C. A similar effect is also observed in some electroplated films at lower temperatures. This investigation attempts to determine the significance of these effects in vacuum-deposited planar films when operated in a practical memory. Reversible and irreversible temperature-induced changes of restore digit current and disturb digit current thresholds, IdRand IdD, respectively, due to pulsed word and digit fields, were measured experimentally for temperatures between 20°C and 135°C. The pulsed fields simulated typical operational word and digit fields. Average threshold variations are given and discussed. Data on average film output variations is also presented.