The dc dielectric strength of uniaxially drawn polyethylene terephthalate (PET) film has been investigated under compressive stresses. The drawn samples are heat-set in a silicone oil bath over a temperature range from 100 to 220°C for durations of 1 and 60 min in order to control the degree of crystallinity of the samples. The dc dielectric strength under no mechanical stress is found to increase with heat-setting temperature regardless of the heat-setting time. The compressive stress value showing maximum dielectric strength under compression has decreased significantly with increase in the heat-setting time and heatsetting temperature. The results obtained are discussed in terms of the morphological and mechanical properties of the samples.