The aging behavior of a polyamide–imide film was investigated. Film samples have been exposed to temperatures from 225° to 350°C for various times and the mechanical and electrical properties measured. This information was used to construct log life plots to gain an insight into the service life of this material. TGA and DTA results coupled with the information from the aging tests indicate that this film can be used at temperatures of 180° to 200°C for extended periods of time. Mechanical properties, especially elongation, of the film deteriorate faster than the electrical properties.