The band alignment at the interface of the heterostructure beta-In2S3/SnO2 has been studied by X-ray photoelectron spectroscopy (XPS). The measurements have been performed on samples obtained under the same experimental conditions as those used to achieve the beta-In2S3/SnO2 ohmic contact. The semi-direct XPS technique used to measure the band offsets allows us to estimate the conduction band discontinuity, DeltaE(c), between beta-In2S3 and SnO2 to -0.45 eV. The band alignment of the beta-In2S3/SnO2 heterostructure being known, we could estimate the Cu(In, Ga)Se-2/beta-In2S3 band alignment using the work function of SnO2 and the electron affinity of Cu(In, Ga)Se, reported in the literature. The conduction band discontinuity at the interface Cu(In, Ga)Se-2/beta-In2S3 has been estimated about 0 eV, which is an interesting result for photovoltaic applications. (C) 2002 Published by Elsevier Science B.V.