Structural and optical properties of In2-2xAl2xS3-3yO3y alloys obtained by the spray pyrolysis technique have been studied. X-ray diffraction (XRD) shows for low compositions (x less than or equal to 0.2) well crystallized films preferentially oriented towards (400) direction corresponding to beta -In2S3 phase; for x > 0.2, the structure becomes amorphous as confirmed by scanning electron microscopy (SEM). Moreover, microanalysis and X-ray photoelectron spectroscopy (XPS) measurements have detected oxygen in the films present in Al2O3 and In2O3 oxides and Al(OH)(3) hydroxides form. On the other hand, from the optical transmission T(lambda) and reflection R(lambda) curves, the study of the absorption coefficient of thin layers versus incident light energy revealed that the value of the band gap energy increases with the composition x according to a parabolic profile.