Carbon fibres were examined for oxidative stability, both in the as-received condition and in a carbon fibre/glass matrix composite, to determine the effect of oxygen partial pressure on their oxidation behaviour. The oxidation data as a function of oxygen partial pressure (0.05, 0.21, and 1.0 atm) were then analysed to determine how the structure of the fibre surface impacts the oxidation behaviour. For the as-received material, it was determined that the data are best described by Temkin-type adsorption kinetics, while the fibres encased in the glass matrix exhibited Langmuir-type kinetics. This relevance of this distinction is discussed.