The oxidative stability of the carbon fiber-reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off-gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190-220 degreesC. Based on the off-gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371 degreesC, thereby marking 371 degreesC to be the highest accelerated aging temperature for its longterm lifetime prediction. Beyond 371 degreesC, different degradation mechanisms would apply.