Kevlar, belonging to the family of high-strength,13; high-modulus aramid fibres, has an extensive range13; of applications . It is likely that while in use, the13; fibres will be exposed either intentionally or accidentally13; to thermal environments, which in turn can alter their properties and performance. In this letter, we report some observations concerning the effect of cumulative thermal exposure on the tensile properties of Kevlar fibre. It must be mentioned that Hindeleh and Abdo [2,3] have already studied the effect of thermal exposures on Kevlar fibres under very specific conditions, namely exposures in an13; atmosphere of nitrogen gas for a duration of 15 min13; at temperatures above 150xB0;C. This study considered13; the effects of thermal exposures that bear a closer13; resemblance to what the fibres would experience in13; their service life, i.e. exposures in an uncontrolled13; atmosphere of air and for durations significantly13; longer than 15 min.