In this study, we evaluated the damage caused by large Ar cluster ion irradiation on polymeric materials, and demonstrated a technique for molecular depth profiling of polymer films. The surface chemical states of the polymers were analyzed with XPS. The chemical states of the polymethyl methacrylate (PMMA) sample etched with Ar monomer ion beams differed significantly from those of the unirradiated sample, but were preserved for the sample etched with Ar cluster ion beams. SIMS depth profiling of the PMMA and polystyrene (PS) films were also carried out by using large Ar cluster ion beams at incident energies between 5.5 and 13 keV, and the effects of incident energy on damage accumulation and depth resolution were investigated. The ratios of the signal intensity at zero fluence to the signal intensity at steady state decreased with increasing incident energy, whereas the depth resolution was little affected by incident energy. Copyright © 2010 John Wiley & Sons, Ltd.