The cermet, Al/Al2O3 deposited on clean Si(1 0 0), was investigated for the mechanism of its transformation induced by laser irradiation. The films were deposited by reactive sputter deposition and, subsequently, irradiated with a single 1064 nm laser pulse in ambient air and 10(-2) Torr vacuum. Characterization included X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. Irradiation in vacuum led to re-distribution of components within the first similar to 35 nm beneath the surface. Irradiation in air increased the concentration of Al2O3 in the same region. Irradiation increased the RMS surface roughness by a factor of 10 in both environments (from 3.5 to 36 nn). On the other hand. Al films irradiated in air do not oxidize measurably with a single laser pulse. Model calculations indicate that a single laser pulse (similar to 16 MW cm(-2)) can increase the local temperature of cermet from 300 to 1200 K. We interpret the observed transformations as a result of local heating and, in air, as accompanying thermal oxidation.