CuInSe2 has emerged as an important photovoltaic semiconductor. The critical importance of stoichiometry changes, interfacial chemical reactions, and compositional variations on cell performance has made the acquisition of reliable quantitative data by surface analysis methods mandatory. In this study, single crystals of CuInSe2 were cleaved in UHV, exposing the (110) plane which is representative of the bulk material. Quantitative AES analysis was performed using both N(E) and dN(E)/dE data, yielding concentration results within 2 at. % of stoichiometric values. The method developed is based upon an independent evaluation of matrix effects using elemental standards and actual density considerations. The effects of Ar+ ion sputtering were investigated for beam energies 0.1<Ep<5.0 kV. Quantitative data for sputter-etched and virgin surfaces have been compared. Oxygen adsorption and In oxidation was observed during exposure to O2 and electron beam irradiation. Polycrystalline thin films of CuInSe2 were also analyzed, and quantitative results have been compared to the single-crystal values.