The oxidation of both, quasicrystalline and crystalline surfaces of an icosahedral Al-Pd-Mn quasicrystal cut perpendicular to its five-fold axis and of Al(111) has been studied by means of X-ray photoelectron spectroscopy, ultraviolet photoemission spectroscopy, low-energy electron diffraction and X-ray photoelectron diffraction. The oxidation of the elements of the alloy is quantified and compared for the different phases and Al(111). The quasicrystalline surface is found to react less with oxygen than the crystalline surface and more rapidly compared to Al(111). The observed behaviour is discussed in terms of the termination of the corresponding surfaces.