The photooxidation of unstabilised isotactic polypropylene (PP) samples (M n 53 kg mol - 1 , M w = 274 kg mol - 1 ) was studied under accelerated ageing conditions (Xenotest, λ ≥ 300 nm; T = 70°C black panel) by infrared (IR) spectrophotometry and size exclusion chromatography. The measurements were made on microtome sections parallel to the exposed surface, in order to establish the degradation profiles due to diffusion control of oxidation kinetics. FromM n and M w values, the numbers n of chain scissions and x of crosslinks were calculated. From IR spectra, the concentrations of carbonyls [CO] absorbing at 1715 cm - 1 and of hydroxyls [OH] absorbing at 3400 cm - 1 were determined. The time variations of these values are discussed in terms of oxidation mechanisms. The variation of polydispersity is discussed in terms of reaction homogeneity.