The interaction of both photoelectrons and X-rays with self-assembled monolayers of n-alkanethiols on gold has been measured using synchrotron radiation as the photon source in the energy range 140-1100 eV. The attenuation length of photoelectrons (lambda) was found to vary from a minimum of similar to 5 Angstrom at an electron kinetic energy (E) of 100 eV up to similar to 23 Angstrom at a kinetic energy of 1000 eV and can be described by the expression lambda = 0.3E(0.64) in the range 300-1000 eV. Exposure of the self-assembled monolayer to X-rays leads to fission of the C-S bond with a cross section of the order of 10(-17) cm(2) which diplays no apparent dependence on the incident photon energy.